Term
| Describe the first part (superior) of the duodenum |
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Definition
| First part (superior) The proximal half is suspended on a mesentery called the hepatoduodenal ligament (right edge of lesser omentum). Therefore, this region is the most moveable. It is located at L1. Duodenal cap or bulb is the term used by radiologists to define the first part of this area. The relations of the first part of the duodenum are of particular importance because of the frequency of duodenal ulcers in this area. When severe, they can ulcerate through the wall and affect adjoining structures. |
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Term
| Describe the second part (descending) of the duodenum |
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Definition
| Second part (descending) is entirely retroperitoneal. The bile duct and pancreatic duct enter its posteromedial wall obliquely and usually unite to form the hepatopancreatic ampulla (ampulla of Vater). Bile stones lodged in this area can block secretion of pancreatic juice, resulting in inflammation of the pancreas due to the proteolytic nature of its enzymes. The ampulla is surrounded by a sphincter (the sphincter of Oddi). Its entrance into the lumen of the duodenum is marked by an elevation, the major duodenal papilla (located at L2). |
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Term
| What is the ampulla of Vater? |
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Definition
| The bile duct and pancreatic duct enter the second part of the duodenum's posteromedial wall obliquely and usually unite to form the hepatopancreatic ampulla (ampulla of Vater). Bile stones lodged in this area can block secretion of pancreatic juice, resulting in inflammation of the pancreas due to the proteolytic nature of its enzymes |
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Term
| Describe the third part (horizontal) of the duodenum |
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Definition
| Third part (horizontal) is crossed anteriorly by superior mesenteric vessels and crosses the vertebrae at L3. |
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Term
| Describe the fourth part (ascending) of the duodenum |
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Definition
| Fourth part (ascending) bends anteriorly to become jejunum at the duodenojejunal junction. It is supported by the suspensory ligament of the duodenum (ligament of Treitz). This ligament sometimes contains smooth muscle and is located at L2. |
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Term
| What is the ligament of Treitz? |
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Definition
| A suspensory ligament ligament of the fourth part of the duodenum. Contains smooth muscle and is located at L2 |
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Term
| What is the major duodenal papilla? |
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Definition
| Located at L2, an elevation in the duodenum marking the sphincter of Oddi |
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Term
| What is the vascular supply to the duodenum? |
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Definition
| Supraduodenal, gastroduodenal, superior and inferior pancreaticoduodenal arteries (from the celiac and superior mesenteric vessels) anastomose frequently with each other. Veins accompanying the arteries drain into the portal system. |
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Term
| What is the general structure of the pancreas? |
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Definition
The pancreas is an exocrine and endocrine organ that is secondarily retroperitoneal. It has four parts:
• Head is found in the curve formed by the 1st, 2nd and 3rd parts of the duodenum. The uncinate process is a prolongation of the head toward the left.
• Neck
• Body
• Tail is located in the splenorenal ligament (usually touches the spleen). |
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Term
| What is the uncinate process? |
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Definition
| A part of the pancreatic head that is a prolongation towards the left. |
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Term
| What are the pancreatic ducts? |
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Definition
| The pancreas has a main pancreatic duct which joins the common bile duct to drain through the ampulla of Vater and the sphincter of Oddi into the second part of the duodenum at the major duodenal papilla. An accessory duct may drain into the duodenum proximal to the main duct through the minor duodenal papilla. |
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Term
| What is the vascular supply to the pancreas? |
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Definition
Anterior and posterior branches of the superior pancreaticoduodenal artery (from gastroduodenal) and the inferior pancreaticoduodenal artery (from superior mesenteric) supply most of the blood to the head of the pancreas.
The splenic artery gives numerous branches to the body and tail of the pancreas.
Numerous veins accompany these arteries and ultimately drain into the portal vein. |
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Term
| What are the two surfaces of the liver? |
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Definition
| The liver has two surfaces, diaphragmatic and visceral, and one sharp inferior border. A portion of the diaphragmatic surface of the liver is directly in contact with the diaphragm and is not covered with peritoneum. This area is referred to as the "bare area" of the liver. |
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Term
| What is the "bare area" of the liver? |
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Definition
| A portion of the diaphragmatic surface of the liver is directly in contact with the diaphragm and is not covered with peritoneum. This area is referred to as the "bare area" of the liver. |
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Term
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Definition
| is on the superior aspect of the liver on the diaphragmatic surface. |
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Term
| Right and left triangular ligaments |
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Definition
| are formed by the junction of the anterior and posterior layers of the coronary ligament. |
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Term
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Definition
| is a peritoneal reflection from the anterior abdominal wall to the sulcus between left and quadrate lobes of liver. It is a remnant of the ventral mesentery. |
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Term
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Definition
is a double-layered peritoneal reflection from the porta hepatis to the lesser curvature of the stomach and to the first part of the duodenum. It has 2 parts:
o Hepatogastric ligament contains the left and right gastric arteries.
o Hepatoduodenal ligament contains the portal vein, bile ducts, and hepatic arteries. |
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Term
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Definition
| is a peritoneal fold from the right triangular ligament to the anterior surface of the right kidney. This ligament is actually a continuation of the posterior layer of the coronary ligament. |
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Term
| What areas and organs are in contact with the liver and may spread disease back and forth? |
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Definition
The liver is in direct contact with the diaphragm at the bare area. Tumors of the lung might spread directly to the liver or vice versa through this route. The following organs are in contact with the visceral surface of the liver and thus are vulnerable to spread of infection from abscesses of the liver:
• Stomach
• Duodenum
• Gallbladder
• Right colic flexure (of colon) |
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Term
| What are the four functional lobes of the liver? |
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Definition
o Right lobe is the largest.
o Quadrate lobe is antero-inferior to the porta hepatis.
o Caudate lobe is postero-superior to the porta hepatis.
o Left lobe is smaller than the right lobe. |
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Term
| What are the two functional lobes of the liver? |
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Definition
Two functional lobes - based on blood supply and biliary drainage
o Right lobe receives blood from right hepatic artery.
o Left lobe includes caudate and quadrate lobes and receives blood from left hepatic and middle hepatic arteries. |
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Term
| Describe the arterial supply of the liver |
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Definition
| About 30% of the blood flow into the liver is through arteries (and the rest is from the portal vein). The common hepatic artery is a branch of the celiac trunk. It usually gives off the proper hepatic artery, which divides into right and left hepatic arteries. Unfortunately, there is great variation in the origin of these vessels, which can be quite disturbing to the surgeon. You should be aware that these variations do occur and that some of the above vessels may arise from the superior mesenteric artery or the left gastric or as a separate branch of the celiac trunk. The caudate and quadrate lobes may receive their blood supply from the middle hepatic artery. This variable artery may arise from either the left or the right hepatic artery. |
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Term
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Definition
| Portal vein enters the porta hepatis and supplies about 70% of blood to the liver. It carries nutrient rich blood from the GI tract and broken down red blood cells from the spleen to the liver for metabolism or storage. It is formed by the union of the superior mesenteric and splenic veins. The inferior mesenteric vein may join either of these two veins or enter at their junction. |
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Term
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Definition
| Hepatic veins drain blood from the liver directly to the inferior vena cava. The right, left and middle hepatic veins are totally enclosed in the hepatic tissue. |
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Term
| The biliary ducts within the liver lobules ultimately come together to make the … |
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Definition
| right and left hepatic ducts that drain the right and left functional halves of the liver. These ducts join to become the common hepatic duct. This duct is joined by the cystic duct from the gallbladder, and their union is referred to as the common bile duct. |
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Term
| Describe the passage of the common bile duct |
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Definition
| This duct travels through the right edge of hepatoduodenal ligament, courses posterior to the first part of the duodenum and through the head of the pancreas. Here, the common bile duct is joined by the main pancreatic duct to make the ampulla of Vater. With appropriate stimulation, bile and pancreatic enzymes are permitted from the ampulla, through the sphincter of Oddi, through the major duodenal papilla, and into the second part of the duodenum. |
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Term
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Definition
| The gallbladder consists of a fundus, body and S-shaped neck. The fundus of the gallbladder lies deep to the lateral border of the right rectus muscle where it intersects the end of the 9th costal cartilage. It is in contact with the liver, the transverse colon and the duodenum. Inflammation of the gallbladder can, therefore, directly inflame these structures. |
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Term
| What is the blood supply to the gallbladder? |
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Definition
| The blood supply of the gallbladder is the cystic artery which usually arises from the right hepatic artery, but on occasion it can arise from the left hepatic, common hepatic, superior mesenteric or celiac arteries. This is an important consideration during removal of the gallbladder. |
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Term
| Characteristics of the jejunum versus ileum |
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Definition
Jejunum (L., empty) : Ileum (L., coiled or twisted)
Shorter (2/5ths) with a thicker wall : Longer (3/5ths) with a thinner wall
Lumen tends to be empty (jejunus = empty) : Lumen tends to be filled
Less fat in mesentery (Deaver's windows) : More fat in mesentery
Circular folds (plicae circulares; valves of Kerckring) are present inside : Circular folds are sparse, almost nonexistent in distal part
Fewer arterial arcades : More arterial arcades
Long straight arteries (vasa recta) : Short straight arteries
Tends to be located superiorly and to the left in the abdomen : Tends to be located inferiorly to the right in the pelvis |
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Term
| Blood supply to the jejunum and ileum |
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Definition
| Numerous intestinal branches of the superior mesenteric artery supply the area. Adjacent intestinal branches anastomose with each other via arcades within the mesentery and within the walls of the intestine. Vasa rectae pass from the arcades to the jejunum and ileum. Venous drainage is through the superior mesenteric vein and to the portal vein. |
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Term
| What are the features that distinguishes the large from the small intestine? |
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Definition
• Taenia coli which are three thickened longitudinal muscle bands along its surface.
• Haustra or sacculations between the taenia coli.
• Appendices epiploicae (epiploic appendages) - small tabs of fat hanging on its external surface. |
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Term
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Definition
| which are three thickened longitudinal muscle bands along the surface of the large intestine |
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Term
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Definition
| Haustra or sacculations between the taenia coli in the large intestine |
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Term
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Definition
| Appendices epiploicae (epiploic appendages) - small tabs of fat hanging on the external surface of the large intestine |
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Term
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Definition
| The cecum is a blind pouch located inferior to the ileocecal valve in the right iliac fossa. It is covered anteriorly with peritoneum, but is usually not suspended on a mesentery. The space posterior to the cecum is called the retrocecal recess. |
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Term
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Definition
| The appendix is a finger-like projection from the cecum. It varies in size from 4-20 cm. and is usually (64%) located in retrocecal recess. It is suspended on a mesentery (mesoappendix) through which the appendicular artery travels. This artery is usually a branch of the ileocolic artery or the posterior cecal artery, and is the sole blood supply of the appendix. McBurney's point is a reference point used to locate the appendix. It is located 1/3 of the distance from the ASIS to the umbilicus. The three bands of the taenia coli may be traced inferiorly along the cecum to locate the appendix, upon which they expand to form the longitudinal coat of the appendix. |
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Term
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Definition
| The ascending colon is secondarily retroperitoneal. It extends from the cecum to the hepatic (right colic) flexure. There are paracolic gutters along the posterior abdominal wall on both sides of the ascending and descending colons. These may allow the spread of infection and/or fluid between abdominal and pelvic cavities. |
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Term
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Definition
| The transverse colon is the longest part of the large intestine. It is suspended on a mesentery, the transverse mesocolon, from the posterior abdominal wall between hepatic and splenic flexures. |
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Term
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Definition
| The descending colon is secondarily retroperitoneal. It extends from the splenic flexure to the sigmoid colon. It is also "sided" by paracolic gutters. The diameter of the large intestine when it is empty can be similar to that of the small intestine. |
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Term
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Definition
| The sigmoid (pelvic) colon occupies the left iliac fossa and connects the descending colon to the rectum. It is suspended by a mesentery (sigmoid mesocolon) from the region of the left common iliac and external iliac vessels. This mesentery is shaped like an inverted V. The sigmoid colon usually has a loop which lies relatively free in the pelvic cavity, and it usually has TWO rows of appendices epiploicae, unlike the remainder of large intestine which has only one row. It varies in length from 6-16 inches. |
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Term
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Definition
| The rectum is the continuation of the large intestine after the sigmoid colon. It begins at level S3, approximately, and is located anterior to the sacrum. It is S-shaped in a coronal plane. Each curve of the "S" projects a transverse rectal fold of mucosa (Houston's valves). There are usually three of these which protrude into the lumen of the rectum and help to support fecal material. The rectal ampulla is a dilation in the distal end of the rectum. The ampulla narrows abruptly at the level of the puborectalis portion of pelvic diaphragm and then makes a sharp posterior bend to become the anal canal. |
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Term
| What are the peritoneal reflection on the rectum? |
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Definition
• Upper third - on the anterior and lateral aspects.
• Middle third - only on the anterior aspect.
• Lower third – none. |
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Term
| What is the rectal ampulla? |
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Definition
| The rectal ampulla is a dilation in the distal end of the rectum. The ampulla narrows abruptly at the level of the puborectalis portion of pelvic diaphragm and then makes a sharp posterior bend to become the anal canal. |
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Term
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Definition
| The anal canal is the constricted distal portion of large intestine extending from the proximal end of the anal columns to the anal orifice. It is surrounded by two anal sphincters. |
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Term
| What are the anal sphincters? |
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Definition
• Involuntary (internal anal sphincter) This is a thickening of the circular layer of smooth muscle in the wall of the intestine (autonomic innervation).
• Voluntary (external anal sphincter) This is a thickening of striated muscle external to the involuntary sphincter. It is innervated by the inferior rectal branch of the pudendal nerve (somatic innervation). |
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Term
| What are the anal columns? |
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Definition
| Anal Columns are about 10 longitudinal mucous membrane folds on the inside of the anal canal. The superior end of the anal columns marks the anorectal junction. |
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Term
| What are the anal valves? |
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Definition
| Anal Valves are small folds of mucosa between the inferior ends of the anal columns which form small pockets called anal sinuses (or crypts). |
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Term
| What is the pectinate line? |
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Definition
| Pectinate Line is a comb-shaped line in the mucosa that marks the location of the anal valves and marks the transition between mucous membrane of the intestine and stratified squamous epithelium of the skin. The white line (intersphincteric groove) marks the division between the internal and external anal sphincters. |
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Term
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Definition
| The opening of the anal canal to the exterior. |
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Term
| What is the arterial supply to the large intestine? |
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Definition
| Rich blood supply is sent to the large intestine via the superior mesenteric artery (ileocolic, right colic and middle colic branches); inferior mesenteric artery (left colic, sigmoidal, and superior rectal branches); internal iliac artery (middle rectal branch); and internal pudendal artery (inferior rectal branch) |
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Term
| What are the anastomoses along the large intestine? |
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Definition
| Arterial anastomoses are numerous and functional (e.g. marginal artery of Drummond) along the mesenteric border of the large intestine. Three points along this marginal artery are relatively weak. They are 1) where the ascending branch of the ileocolic joins the descending branch of the right colic; 2) where the left branch of the middle colic joins the ascending branch of the left colic; and 3) just after the last sigmoidal branch is given off. |
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Term
| What are internal hemorrhoids? |
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Definition
| Internal hemorrhoids are varicosities of the tributaries of superior rectal veins and are covered by mucous membrane. |
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Term
| What are external hemorrhoids? |
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Definition
| External hemorrhoids are painful because they are varicosities of the inferior rectal veins and are covered by skin. |
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Term
| Where is the anal canal derived from embryologically? |
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Definition
| The anal canal superior to the pectinate line and the rectum both develop from the hindgut (endoderm), whereas the anal canal inferior to the pectinate line is derived from ectoderm. |
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Term
| Because of its hindgut origin, the upper part of the anal canal and the rectum are supplied by arterial blood from the ... |
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Definition
| superior rectal artery, a branch of the inferior mesenteric artery. |
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Term
| Sensation from the superior anal canal and rectum is … |
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Definition
| visceral (vague and relatively pain free), because of its derivation from hindgut. |
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Term
| What is the portocaval anastomosis and its significance? |
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Definition
| Between tributaries of the caval system (inferior rectal veins) and portal system (superior rectal veins). Any abnormal increase in pressure in the valveless portal system may be one of numerous causes of hemorrhoids. |
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Term
| What is the caval system? |
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Definition
| The caval system is that which receives venous blood from the head, neck, extremities, and body wall and collects it via the superior and inferior vena cavae before draining it into the right atrium. |
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Term
| What is the portal system? |
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Definition
| The portal system is another venous network that begins in small venules all along the intestinal tract and ends in venous sinusoids in the liver. Here the nutrient rich blood is processed and detoxified before leaving the liver via central veins which coalesce into the hepatic veins. The right, left, and middle hepatic veins are enclosed within the liver and empty into the inferior vena cava (which is partially enclosed within the liver). The portal system is a VALVELESS network of veins. This means that blood can flow in any direction depending on pressure differences within the system. |
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Term
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Definition
| The portal vein is formed by the union of superior mesenteric and splenic veins. The inferior mesenteric vein can drain into the splenic vein or into the place where the splenic vein joins the superior mesenteric vein. Other tributaries to the portal vein include veins from the duodenum, lesser curvature of the stomach and lower esophagus, the gallbladder, and umbilical region. |
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Term
| What is the importance of portocaval anastomoses? |
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Definition
| For a number of reasons the return of blood to the liver from the portal system may be blocked. Some of these reasons include formation of blood clots in the portal vein or scarring of the liver (cirrhosis) causing compression of small vessels in the liver tissue. As a result, hydrostatic pressure increases in the portal vein and vessels that drain into it become distended with blood. This can lead to ascites (accumulation of fluid in the peritoneal cavity) among other things. Fortunately, there are several regions that are drained by both portal and caval veins. These alternative pathways are known as portocaval anastomoses. Backup of pressure at these sites may cause dilated veins which are prone to rupture. |
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Term
| What are important areas of portocaval anastomoses? |
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Definition
| Lower end of the esophagus, anal canal, umbilicus, places where abdominal viscera are retroperitoneal, bare area of the liver |
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Term
| Portocaval anastomoses of the lower end of the esophagus |
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Definition
| The esophageal veins can drain either to the left gastric vein and then to the portal vein; or to the azygos vein and then to superior vena cava. Distended veins in this area are referred to as esophageal varices. |
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Term
| Portocaval anastomoses of the anal canal |
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Definition
| Superior rectal veins can drain via the inferior mesenteric vein to the portal vein; and the middle and inferior rectal veins can drain to internal iliac veins which drain via common iliac veins into the inferior vena cava (caval system). |
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Term
| Portocaval anastomoses of the umbilicus |
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Definition
| Paraumbilical veins drain through the falciform ligament to the portal vein or via systemic veins on the anterior abdominal wall to the caval system. Distended veins around the umbilicus may present as the caput medusae. |
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Term
| Portocaval anastomoses in places where abdominal viscera are retroperitoneal |
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Definition
| Veins in the walls of posterior viscera can drain either into the portal system or into veins of the adjacent abdominal wall or diaphragm. |
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Term
| Portocaval anastomoses in the bare area of the liver |
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Definition
| Here there is no visceral or parietal peritoneum separating the liver from the diaphragm and venous communications are common. |
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Term
| Boundaries and muscles of the posterior abdominal wall |
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Definition
| The posterior abdominal wall extends from the twelfth rib to the pelvic brim. Vertebrae T12 to L5 are located in the midline posteriorly and the iliolumbar and sacroiliac ligaments anchor the ilium of the hip bone to the 5th lumbar vertebra and sacrum. Muscles of the posterior abdominal wall include diaphragm, psoas major and minor (if present), quadratus lumborum, iliacus, and transversus abdominis. |
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Term
| The kidneys, ureters and suprarenal glands are deeply embedded in and supported by … |
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Definition
| subserous fascia and fat on the posterior wall between peritoneum and the transversalis fascia lining the abdominal cavity. |
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Term
| What do the aorta and inferior vena cava bifurcate into? |
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Definition
| Common iliac vessels, which bifurcate into external and internal iliac vessels before leaving the posterior abdominal wall |
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Term
| What are the three parts of the diaphragm? |
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Definition
| Sternal, costal, and lumbar |
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Term
| What is the lumbar part of the diaphragm? |
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Definition
| The lumbar part arises from thickenings of transversalis fascia called medial and lateral arcuate ligaments (aka, lumbocostal arches) and from crura. |
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Term
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Definition
| The right and left crura have tendinous origins from some of the lumbar vertebrae and blend in with the anterior longitudinal ligament of the vertebral column. The two crura pass ventrally and meet in the midline to form the median arcuate ligament, across the ventral aspect of the aorta. The medial arcuate ligament is a thickening of transversalis fascia where the psoas major muscle passes posterior to the diaphragm. |
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Term
| What is the median arcuate ligament? |
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Definition
| Formed by the two diaphragmatic crura meeting in the midline |
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Term
| What is the lateral arcuate ligament? |
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Definition
| The lateral arcuate ligament is the fascial thickening where quadratus lumborum muscle passes posterior to the diaphragm. |
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Term
| What is the central tendon of the diaphragm? |
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Definition
| The central tendon of the diaphragm is a strong aponeurosis situated near the center of the muscle and is partially blended with the fibrous pericardium superior to it. |
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Term
| What is the arterial supply to the diaphragm? |
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Definition
| Blood supply is from the pericardiacophrenic, musculophrenic, lower intercostal and superior and inferior phrenic arteries. |
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Term
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Definition
| The kidneys are paired retroperitoneal organs surrounded by a protective layer of subserous fascia and fat. The superior poles are at vertebral level T12 and the inferior poles at L3. The right kidney is slightly lower than the left because of the liver. |
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Term
| What is the blood supply to the kidneys? |
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Definition
• Renal arteries arise directly from the aorta. Usually there is only one artery to each kidney, but sometimes (25%) there may be multiple arteries.
• Renal veins drain into the inferior vena cava after receiving tributaries from the suprarenal glands. The left renal vein also receives the left gonadal vein.
• Vessels and nerves enter and leave the kidney through the renal hilus at L1. |
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Term
| What is the general structure of the kidneys? |
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Definition
| Deep to the fibrous capsule, the renal cortex is the outer layer of the kidney. At various intervals, it projects into the deeper layer (medulla) as renal columns. The renal medulla (pyramids) are the triangular shaped masses of tissue between the renal columns. The apices of the renal pyramids project into numerous minor calyces. Urine is collected in these and then drains into larger conduits, called major calyces. Two or three major calyces unite to form the renal pelvis which is a funnel-shaped dilation of the superior end of the ureter. The ureter then conveys the urine to the urinary bladder. |
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Term
| The right and left ureters are embedded in … |
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Definition
| subserous fascia behind parietal peritoneum and are crossed anteriorly by the gonadal arteries. |
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Term
| Where do ureters enter the pelvic cavity? |
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Definition
| Cross anteriorly to the bifurcation of the common iliac vessels |
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Term
| Where do ureters run in the pelvis? |
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Definition
| Within the pelvis, the ureters pass deep to the peritoneum, ventral to the internal iliac arteries, and reach the lateral angles of the bladder. They run obliquely through the bladder wall and open by slit-like apertures into the cavity of the bladder. |
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Term
| What are the three anatomical narrowings of the ureter where kidney stones may be caught? |
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Definition
| the ureteropelvic junction (where the pelvis of the kidney becomes the ureter), the pelvic brim, and at the entrance of the ureters into the bladder. |
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Term
| What is the blood supply to the ureters? |
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Definition
| Blood supply to the ureters is from the aorta, renal, common iliac and inferior vesical arteries. |
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Term
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Definition
| The urinary bladder is a musculomembranous sac which acts as a reservoir for urine. It is located posterior to the pubic symphysis; but its size, position, and relationships vary according to the amount of fluid it contains. It has an apex superiorly (attached to the obliterated urachus) and a neck inferiorly (attached to the urethra). |
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Term
| What are the ligaments of the urinary bladder? |
|
Definition
Ligaments - The bladder is held in position by ligamentous condensations of subserous fascia.
• In the FEMALE, the attachments are directly between bladder and pubis and are called the pubovesical ligaments.
• In the MALE, because the prostate is firmly bound to the bladder, these attachments are between the prostate and the pubic bone and are named puboprostatic ligaments.
• The bladder is secured posteriorly to the side of the rectum and sacrum by rectovesical ligaments. |
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Term
| innervation of the urinary bladder |
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Definition
| Innervation of the urinary bladder comes from pelvic splanchnic nerves (parasympathetic) and sacral splanchnic nerves (sympathetic). Parasympathetic fibers activate the detrusor muscle; sympathetic fibers activate the trigone and an involuntary sphincter. Perineal nerves containing somatic motor fibers to a voluntary sphincter provide some voluntary control of micturition. |
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Term
| blood supply to the urinary bladder |
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Definition
| from superior and inferior vesical arteries from branches of the internal iliac artery |
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Term
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Definition
| The mucous membrane lining the bladder is loosely attached to the muscular coat and appears wrinkled or folded when the bladder is contracted except over a small triangular area termed the trigone which is immediately superior and posterior to the urethral orifice. Here the mucous membrane is firmly bound to the muscular coat (i.e., detrusor muscle) and is smooth. The anterior angle of the trigone is formed by the internal orifice of the urethra; its posterolateral angles are formed by the orifices of the ureters. Stretching between the 2 ureteral orifices is the interureteric fold forming the base of the trigone. |
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Term
| What are the two sphincters of the urethra? |
|
Definition
| The involuntary sphincter is the thickened smooth muscle at the neck of the bladder which is under autonomic control. The voluntary sphincter is made of striated muscle and is located in the urogenital diaphragm in the perineum. |
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Term
| What is the lumbar plexus? |
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Definition
| The lumbar plexus is formed by ventral rami of the first 3 and the greater part of the 4th lumbar nerves with a communication from the 12th thoracic nerve. It is on the internal surface of the posterior abdominal wall, ventral to the transverse processes of the lumbar vertebrae. Its branches pierce the psoas muscle. |
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Term
| What are the branches of the lumbar plexus? |
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Definition
1. Iliohypogastric (L1 and a small contribution from T12)
2. Ilioinguinal (L1)
3. Genitofemoral (L1, 2)
4. Lateral femoral cutaneous (L2, 3)
5. Obturator (L2. 3, 4)
6. Accessory obturator (L3, 4) (when present, 29%)
7. Femoral (L2, 3, 4) |
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Term
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Definition
(L1, T12)
It innervates muscles of the anterior abdominal wall and then divides into an anterior and a lateral cutaneous branch. The lateral branch supplies the skin in the gluteal region and the anterior branch pierces the transversus abdominis and the aponeurosis of the external oblique about 2 cm superior to the superficial inguinal ring. It provides cutaneous innervation in that region. |
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Term
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Definition
(L1)
It follows the same course as the iliohypogastric, but is more inferior in position and accompanies the spermatic cord through the superficial inguinal ring. It is distributed to the skin over the medial part of the thigh and the scrotum (anterior scrotal nerve) and the mons pubis and labia majora (anterior labial nerve). Both ilioinguinal and iliohypogastric nerves innervate external and internal oblique muscles as well as transversus abdominus muscle and underlying peritoneum. |
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Term
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Definition
(L1, 2)
On the surface of the psoas muscle, it divides into a genital and a femoral branch.
• Genital branch passes through the deep and superficial inguinal rings. It lies against the dorsal aspect of the cord and supplies motor innervation to the cremaster muscle and sensory fibers to the skin of the scrotum and adjacent thigh. In the female it accompanies the round ligament of the uterus to the skin of the labia majora.
• Femoral branch passes deep to the inguinal ligament with the external iliac artery. It enters the femoral sheath, then pierces the sheath and fascia lata (deep fascia of the thigh) to supply the skin of the thigh over the femoral triangle. |
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Term
| lateral femoral cutaneous nerve |
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Definition
| (L2, 3) is sensory to the lateral aspect of the thigh. It normally passes just medial to the ASIS. |
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Term
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Definition
| (L2, 3, 4) provides motor innervation to the adductor muscles of the thigh and cutaneous branches to the medial thigh. |
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Term
| accessory obturator nerve |
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Definition
| (L3, 4) is present in 29% of the population and supplies motor innervation to the pectineus muscle of the thigh. |
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Term
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Definition
| (L2, 3, 4) is the largest branch of the lumbar plexus and the principal nerve of the anterior part of the thigh. It supplies motor innervation to muscles of the anterior thigh and sensory innervation to anterior thigh and medial leg. |
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Term
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Definition
| These are collections of postganglionic sympathetic cell bodies which are located around the bases of the major arteries on the abdominal aorta (only). Incoming preganglionic sympathetic nerves (e.g., greater, lesser, least and lumbar splanchnic nerves) from the sympathetic chain ganglia of T5-L2 enter the prevertebral ganglia and synapse on postganglionic sympathetic cell bodies. Postganglionic fibers are closely applied to the sides of the arteries (with which the ganglia are associated) and get distributed with the branches of the arteries to whichever organs they supply. The major prevertebral ganglia are the celiac ganglion complex and the inferior mesenteric ganglion. The celiac ganglion complex is a conglomeration of several smaller ganglia. These smaller ganglia may or may not be distinguishable and usually include celiac, superior mesenteric, aorticorenal, and renal ganglia. All of these ganglia are interconnected. |
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Term
| Describe preganglionic parasympathetic fibers passing through prevertebral ganglia |
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Definition
| Preganglionic parasympathetic fibers from the vagus nerve pass through each of the ganglia comprising the celiac ganglion complex and are distributed with the blood vessels until they reach their appropriate terminal ganglia in the wall of their target organs. The preganglionic parasympathetics passing through the inferior mesenteric (sympathetic) ganglion are derived from S2, 3, and 4 via the pelvic splanchnic nerves. |
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Term
| bilateral continuations of the sympathetic chain ganglia |
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Definition
| There is a sympathetic chain ganglion attached to the ventral ramus (via a gray ramus communicans) of every spinal nerve (from C1 to Co1). Splanchnic nerves from these sympathetic chain ganglia are mostly postganglionic sympathetic fibers which may pass through a prevertebral ganglion or travel directly to the organs via the arteries. Below the level of the inferior mesenteric ganglion, there are no more prevertebral ganglia. Therefore, splanchnic nerves from sympathetic ganglia inferior to the level of L4 or L5 will pass directly to most of the organs of the pelvis and perineum. These (sympathetic) splanchnic nerves descend into the pelvis and get intermingled with pelvic (parasympathetic) splanchnic nerves which are ascending out of the pelvis. The mixture of these nerves all around the internal iliac and common iliac arteries, and aortic bifurcation forms the pelvic plexus and hypogastric plexus. |
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Term
| innervation of the adrenal medulla |
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Definition
| the chromaffin cells of the adrenal medulla secrete epinephrine and norepinephrine (just like postganglionic sympathetic cell bodies). They are stimulated by preganglionic sympathetic fibers that travel in the lesser and least splanchnic nerves and pass through the aorticorenal ganglion (without synapsing). The “fight or flight” hormones are released directly into the blood stream. |
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Term
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Definition
| PELVIC SPLANCHNIC NERVES are preganglionic parasympathetic fibers whose cell bodies are located in the gray matter at spinal cord levels S2, 3, and 4. These preganglionic fibers leave the lateral horn, and subsequently pass through the ventral horn, ventral root, spinal nerve, and ventral ramus associated with S2, 3, and 4. These fibers then directly branch off the ventral rami as pelvic splanchnic nerves. These pelvic splanchnics mingle into the pelvic plexus and get distributed on blood vessels to reach the organs of the pelvis and perineum; or they ascend out of the pelvis to reach the aorta (via the hypogastric plexus or on blood vessels), and then pass through the inferior mesenteric ganglion to get distributed with that vessel. |
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Term
| The vagus nerve innervates all structures related to the GI tract from the esophagus to the … |
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Definition
| splenic flexure of the large intestine. S2, 3, and 4 (via pelvic splanchnic nerves) regulate the rest of the GI tract from the splenic flexure to the anus. The vagus also innervates the kidneys, testes, and ovaries. |
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Term
| Pelvic splanchnics are responsible for … |
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Definition
| all urogenital structures not innervated by the vagus and is responsible for erection. |
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Term
| Tracheo-esophageal fistula: |
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Definition
| When the elongating lung bud (of pharyngeal gut origin) and the adjacent elongating esophagus fuse, to focally share a lumen |
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Term
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Definition
| The esophagus ends in a blind pouch |
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Term
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Definition
| Pancreatic tissue completely surrounds and narrows the duodenum. This occurs when pieces of pancreas are deposited along the path of the migrating ventral pancreas. |
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Term
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Definition
| Persistence of a lumen of the proximal portion of the vitelline duct located in the ileum. The mucosa can have gastric glands, which can produce acid and cause ulceration and bleeding. The anomaly is present in 2-4% of the population. |
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Term
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Definition
| Persistence of physiological herniation, with abdominal organs remaining within the confines of the umbilical cord. About half of the affected individuals have a chromosomal anomaly. |
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Term
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Definition
| Persistence of physiological herniation, but less severe than omphalocele. A portion of intestines protrudes at the umbilicus but is covered with skin and subcutaneous tissue. |
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Term
| What systems does the yolk sac contribute to? |
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Definition
| The yolk sac, of endodermal origin, contributes to more organ systems than any other embryologic structure. These systems include hematopoietic, immune, endocrine, reproductive, urinary, auditory, respiratory and finally digestive. |
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Term
| At four weeks, what does the yolk sac reconfigure into? |
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Definition
| Within the first four weeks, the yolk sac reconfigures its shape from a sac to a tube with two long, relatively narrow-necked diverticula, the vitelline duct and the allantois. The gut tube is divided into the pharyngeal gut (buccopharyngeal membrane to lung bud); foregut (after lung bud to hepatic diverticulum); midgut (after hepatic diverticulum to proximal 2/3rds of colon) and hindgut (distal 1/3rd of colon to cloacal membrane). |
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Term
| What is the vitelline duct? |
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Definition
| Joins the yolk sac to the midgut lumen of the developing fetus |
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Term
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Definition
| Helps the embryo exchange gases and handle liquid waste |
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Term
| How is the gut tube divided in the embryo? |
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Definition
| The gut tube is divided into the pharyngeal gut (buccopharyngeal membrane to lung bud); foregut (after lung bud to hepatic diverticulum); midgut (after hepatic diverticulum to proximal 2/3rds of colon) and hindgut (distal 1/3rd of colon to cloacal membrane). |
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Term
| What is the foregut in an embryo? |
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Definition
| From after lung bud to hepatic diverticulum |
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Term
| What is the midgut in an embryo? |
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Definition
| After hepatic diverticulum to proximal 2/3rds of colon |
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Term
| What is the hindgut in an embryo? |
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Definition
| Distal 1/3rd of colon to cloacal membrane |
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Term
| What is the pharyngeal gut in an embryo? |
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Definition
| extends buccopharyngeal membrane to lung bud |
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Term
| What is the dorsal mesentery in an embryo? |
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Definition
| A dorsal mesentery, made up of splanchnic mesoderm suspends the foregut, midgut and hindgut along the midline of the embryo. The dorsal mesentery enlarges greatly to form the greater omentum. The dorsal mesentery of the stomach is sometimes called the dorsal mesogastrium. |
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Term
| What is the ventral mesentery in an embryo? |
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Definition
| Ventral mesentery tethers just the foregut along the midline. There is no ventral mesentery beyond the hepatic diverticulum. The ventral mesogastrium becomes the lesser omentum and falciform ligament. |
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Term
| How does the stomach develop embryologically? |
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Definition
| The esophagus simply elongates to keep pace with the growth of the embryo. A fusiform swelling just distal to the esophagus forms the stomach. The stomach then rotates clockwise 90° from the vantage point of the embryo, and then flattens and moves over to the left side of the upper abdomen. As the stomach shifts to the left, the duodenum shifts to the right, and its dorsal mesentery fuses with the posterior abdominal wall. Thus, the proximal duodenum becomes retroperitoneal. |
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Term
| How does the proximal duodenum become retropetironeal? |
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Definition
| In the embryo, as the stomach shifts to the left, the duodenum shifts to the right, and its dorsal mesentery fuses with the posterior abdominal wall. Thus, the proximal duodenum becomes retroperitoneal. |
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Term
| What is the hepatic diverticulum? |
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Definition
| The hepatic diverticulum is a ventral structure and has three buds – the liver bud, the gallbladder bud and the ventral pancreas bud. |
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Term
| What is the vascular supply of the foregut in an embryo? |
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Definition
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Term
| What is the vascular supply of the midgut in an embryo? |
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Definition
| superior mesenteric artery |
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Term
| What is the vascular supply of the hindgut in an embryo? |
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Definition
| inferior mesenteric artery |
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Term
| What is the vascular supply of the pharyngeal gut in an embryo? |
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Definition
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Term
| What is the ventral mesogastrium? |
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Definition
| The liver and gallbladder bud stay close together and grow into the ventral mesogastrium (ventral mesentery in the region of the stomach) and then revolve clockwise, from the embryo’s vantage point, around the axis of the gut to assume their final position in the right side of the abdomen. |
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Term
| How is the liver related to the septum transversum? |
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Definition
| septum transversum is immediately above the liver, and the liver does indeed grow into portions of septum transversum |
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Term
| What is the dorsal pancreas bud? |
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Definition
| Located just opposite of the gut tube where the hepatic diverticulum arises, the dorsal pancreas bud arises in the dorsal mesogastrium. This dorsal pancreas bud is joined by the ventral pancreas bud, which had revolved around the gut tube clockwise, 270°. Then, both the dorsal and ventral pancreas continue another 90% of revolution to end up in the left side. Both fuse together and also fuse to the posterior abdominal wall to become retroperitoneal. |
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Term
| How do the midgut and hindgut grow and what changes occur in these regions during development? |
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Definition
| By lengthening. For a time, this lengthening exceeds the volume of the abdominal cavity, such that the bowel loops herniate out of the abdomen, into the connecting stalk. This physiologic herniation persists until about 10 weeks. As the loops of bowel return to the abdomen, they revolve around the axis of the superior mesenteric artery, which is the main artery of the midgut. This revolution occurs clockwise from the vantage point of the embryo and is 270° in extent. The dorsal mesentery of the ascending and descending colon fuses to the posterior abdominal wall. The cecum ends up in the right lower quadrant. Where the retroperitoneal duodenum (see above) perforates through the dorsal mesentery of the colon to connect with the rest of the small bowel is called the ligament of Treitz. |
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Term
| What is physiologic herniation in an embryo? |
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Definition
| The midgut and hindgut grow by lengthening. For a time, this lengthening exceeds the volume of the abdominal cavity, such that the bowel loops herniate out of the abdomen, into the connecting stalk. This physiologic herniation persists until about 10 weeks. |
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Term
| What happens after physiologic herniation in the embryo? |
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Definition
| As the loops of bowel return to the abdomen, they revolve around the axis of the superior mesenteric artery, which is the main artery of the midgut. This revolution occurs clockwise from the vantage point of the embryo and is 270° in extent. The dorsal mesentery of the ascending and descending colon fuses to the posterior abdominal wall. The cecum ends up in the right lower quadrant. Where the retroperitoneal duodenum (see above) perforates through the dorsal mesentery of the colon to connect with the rest of the small bowel is called the ligament of Treitz. |
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Term
| What is the ligament of Treitz? |
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Definition
| Where the retroperitoneal duodenum perforates through the dorsal mesentery of the colon to connect with the rest of the small bowel is called the ligament of Treitz. |
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Term
| What is the urorectal septum? |
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Definition
| At 6-7 weeks, the distal hindgut (destined to be the rectum) and the allantois (destined to be the bladder) are separated by a shelf of splanchnic mesoderm, simply called the urorectal septum. |
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Term
| What is the role of goblet cells in the small intestine? |
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Definition
| The role of goblet cells is to secrete mucus, a viscous fluid composed primarily of highly glycosylated proteins called mucins suspended in a solution of electrolytes. Mucus serves many functions, including protection against shear stress and chemical damage, and, especially in the respiratory tree, trapping and elimination of particulate matter and microorganisms. |
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Term
| What staining technique allows for easy visualization of Goblet cells? |
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Definition
| periodic acid-Schiff (PAS) technique, which stains glycoproteins, including mucins, bright purple |
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Term
| How are Goblet cells polarized? |
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Definition
| Their nucleus is at the base of the cell, along with organelles such as mitochondria, endoplasmic reticulum and Golgi. The remainder of the cell is filled with membrane-bound secretory granules filled with mucus. |
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Term
| What are the general functions of Paneth cells and where are they located? |
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Definition
Paneth cells are part of the epithelial lining of the small intestines, where they are found at the base of the crypts of Lieberkühn. Although the precise function of Paneth cells is unclear, lysozyme has been found in the secretory granules, Golgi apparatus and rough ER, and immunoglobulins (IgA and IgG) have been demonstrated in the cell cytoplasm. The presence of lysozyme (an enzyme with limited bactericidal activity that is enhanced in the presence of immunoglobulins and complement) combined with the phagocytic capability of Paneth cells, suggests they are involved in regulation of the microbial flora of the small intestine. The highest concentrations of antimicrobial agents from Paneth cells are reached in the base of the crypt from where the intestinal stem cells continually regenerate the absorptive epithelium of the villi, hence the proposal that these cells guard the gut hatchery. Cationic trypsin immunoreactivity has been demonstrated in human Paneth cells, indicating a possible role in secretion of digestive enzymes, and their content of heavy metals, particularly zinc, suggests a role in the elimination of metals. Unlike
other cells in the intestinal epithelium, Paneth cells have a long lifespan. |
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Term
| What are the three main sections of the large intestine? |
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Definition
| Cecum, colon, and rectum. |
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Term
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Definition
The longitudinal muscle fibers on the outside of the large intestine converge to form three distinct bands called teniae coli. The tenia
coli begin at the base of the vermiform appendix and are shorter than the length of the large intestine so that the intestine becomes bunched up. |
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Term
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Definition
| Bulges seen on the large intestine |
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Term
| What are epiploic appendices? |
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Definition
| Small, fatty sacs of peritoneum found on the colon |
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Term
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Definition
| The cecum is a blind sac at the lower end of the ascending colon. The contents of the ileum empty into it through the ileocecal valve. The lips of the valve are oriented horizontally and prevent reflux of cecal contents into the ileum. |
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Term
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Definition
| The vermiform appendix is a narrow part of the large bowel that hangs from the apex of the cecum. The submucosa of the appendix contains much lymphoid tissue indicating that it may play a role in fighting infection. The precise function of the appendix has not yet been determined. |
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Term
| What is the name of the small mesentery of the appendix? |
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Definition
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Term
| What happens in appendicitis? |
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Definition
The lumen of the appendix is essentially a narrow cul-de-sac that is continuous with the lumen of the cecum. When the appendix is inflamed, swelling in the wall of the appendix can restrict flow between the lumens of the cecum and appendix. As the bacterial load increases, inflammation in the wall of the appendix increases. In turn, wall tension increases, blood supply is cut off, gangrene can
set in and the wall can perforate. |
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Term
| What are the four parts of the colon? |
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Definition
| Ascending, transverse, descending, and sigmoid |
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Term
| What is the ascending colon? |
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Definition
the ascending colon, which is retroperitoneal, extends from the cecum to the right colic (hepatic)
flexure |
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Term
| What is the transverse colon? |
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Definition
| The transverse colon is intra-peritoneal and passes transversely from the right colic flexure to the left colic (splenic) flexure. It has a long mesentery (the mesocolon) that allows for considerable displacement of this part of the colon. The transverse colon is attached to the stomach by the gastrocolic ligament on the underside of the greater omentum. |
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Term
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Definition
| the ascending colon is retroperitoneal, extends from the cecum to the right colic (hepatic) flexure |
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Term
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Definition
| The transverse colon is intra-peritoneal and passes transversely from the right colic flexure to the left colic (splenic) flexure. It has a long mesentery (the mesocolon) that allows for considerable displacement of this part of the colon. The transverse colon is attached to the stomach by the gastrocolic ligament on the underside of the greater omentum. |
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Term
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Definition
| The descending colon passes from the splenic flexure to the sigmoid colon. The descending colon is retroperitoneal. |
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Term
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Definition
| The sigmoid colon has a V-shaped mesentery and is shaped like the letter S, hence its name. The mesentery of this portion of the colon is called the sigmoid mesocolon. The sigmoid colon is continuous with the rectum, which is in turn continuous with the anal canal. |
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Term
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Definition
| The rectum is a 12 cm long section of large intestine that connects the sigmoid colon to the anal canal. This is a segment of intestine that acts to store fecal matter until such a time when defecation (taking a dump) is convenient and socially acceptable. The rectum, which begins at the third segment of the sacrum, follows the curve of the sacrum and coccyx to about 2 cm below the tip of the coccyx, where it turns posteriorly to become the anal canal. This is the area where the sling of the puborectalis (part of the pelvic diaphragm) is located. The arterial supply to the rectum is unique because it receives blood supply from mesenteric as well as the iliac arteries |
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Term
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Definition
| The anal canal is the terminal portion of the digestive tract. It begins as the lower, dilated end of the rectum converges to form a narrow canal that is 3-4 cm long. The sides of the anal canal are surrounded and padded by the fatty, compliant tissue of the ischiorectal fossa. |
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Term
| What is the histological nature of the upper half of the anal canal? |
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Definition
The upper half of the anal canal has a mucosal columnar epithelial cell lining, similar to the lining of the rectum, and is sensitive to distension and pressure. The mucosa of the upper half of the anal canal has 6-10 vertical folds called anal columns that contain the terminal branches of the superior rectal veins, called the hemorrhoidal veins. Small transverse folds of mucous membrane, called anal valves, join the lower ends of the anal columns. This line of attachment is called the
pectinate line. |
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Term
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Definition
| The mucosa of the upper half of the anal canal has 6-10 vertical folds called anal columns that contain the terminal branches of the superior rectal veins, called the hemorrhoidal veins. |
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Term
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Definition
| In the anal canal, small transverse folds of mucous membrane, called anal valves, join the lower ends of the anal columns. |
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Term
| What are the anal sphincters? |
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Definition
| The anal orifice is bridled by a pair of sphincters, the external anal sphincter and the internal anal sphincter. The external anal sphincter is made of skeletal muscle and is continuous with fibers of the levator ani. This sphincter is under voluntary control and is innervated by the inferior rectal branches of the pudendal nerves. The internal anal sphincter is a thickening of the circular smooth muscle of the rectum. The internal anal sphincter is not under voluntary control and is innervated by the autonomic nervous system. |
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Term
| How are hemorroids formed? |
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Definition
| The superior rectal veins (which drain into the portal venous system) anastomose with the inferior rectal veins (which drain into the internal pudendal veins of the systemic system). Repetitive straining during defecation can result in a distention of the interposed hemorrhoidal veins, a condition known as hemorrhoids, or piles. |
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Term
| What is the most obvious histological difference between the large and small intestine? |
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Definition
| The histology of the large intestine differs from that of the small intestine in a number of ways, the most obvious of which is that there are no intestinal villi in the large intestine, and Paneth cells are not present in the base of the colonic crypt glands. Another distinguishing feature of the colonic epithelium is the high prevalence of goblet cells. |
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Term
| What are the histological differences between small and large intestines? |
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Definition
| The histology of the large intestine differs from that of the small intestine in a number of ways, the most obvious of which is that there are no intestinal villi in the large intestine. The mucosa of the large intestine does contain crypts of Lieberkühn, which are often referred to as colonic glands. Unlike the tubular glands of the small intestine, the colonic glands do not contain Paneth cells. While enterocytes, or absorptive cells, are the most numerous cell type, the mucosa of the large intestine contains many more goblet cells than are found in small intestine. Enteroendocrine cells are present, primarily in the lower halves of the colonic glands, throughout the length of the large intestine. Stem (regenerative) cells are located near the base of the crypts, and their mitotic activity results in the replacement of colonic epithelium every 6-7 days. |
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Term
| How do the submucosal and muscularis externa layers of the large and small intestine differ? |
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Definition
| The submucosal and muscularis externa layers of the large intestine resemble those of the small intestine with the exception that the longitudinal muscle is gathered into three bands, the teniae coli, rather than forming a continuous sheet. |
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Term
| What are the histological properties of the colon? |
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Definition
• EPITHELIUM: Simple columnar (w/ goblet cells); Surface absorptive cells, goblet cells, enteroendocrine cells;
• LAMINA PROPRIA: Crypts of Lieberkuhn in lamina propria
• GLAND CELLS: Surface absorptive cells, goblet cells, regenerative cells, enteroendocrine cells
• MUSCULARIS MUCOSA: Fairly thin
• SUBMUCOSA: no glands
• MUSCULARIS EXTERNA: Inner circular, outer longitudinal
• *** Serosa and adventitia |
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Term
| What are the histological properties of the appendix? |
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Definition
• EPITHELIUM: Simple columnar (w/ goblet cells); Surface absorptive cells, goblet cells, enteroendocrine cells;
• LAMINA PROPRIA: Crypts of Lieberkuhn and Peyer’s Patches
• GLAND CELLS: Surface absorptive cells, goblet cells, regenerative cells, enteroendocrine cells, Paneth cells
• MUSCULARIS MUCOSA: Fairly thin
• MUSCULARIS EXTERNA: Inner circular, outer longitudinal
• *** Serosa only |
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Term
| What are the histological properties of the rectum? |
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Definition
• EPITHELIUM: Simple columnar (w/ goblet cells); Surface absorptive cells, goblet cells, enteroendocrine cells;
• LAMINA PROPRIA: Shallow crypts of Lieberkuhn, lymphoid nodules
• GLAND CELLS: Surface absorptive cells, goblet cells, regenerative cells, enteroendocrine cells
• MUSCULARIS MUCOSA: Fairly thin
• SUBMUCOSA: no glands
• MUSCULARIS EXTERNA: Inner circular, outer longitudinal
• *** Adventitia only |
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Term
| What are the histological properties of the anal canal? |
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Definition
• EPITHELIUM: Simple cuboidal; squamous non-keratinized; stratified sqamous keratinized
• LAMINA PROPRIA: Rectal columns, circumanal glands, at anus hair follicles and sebaceous glands
• GLAND CELLS: Surface absorptive cells, goblet cells, regenerative cells, enteroendocrine cells
• MUSCULARIS MUCOSA: Fairly thin
• SUBMUCOSA: no glands, internal and external hemorrhoidal plexuses
• MUSCULARIS EXTERNA: Inner circular (forms internal anal sphincter), outer longitudinal
• *** Adventitia only |
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Term
| Where is the pancreas located? |
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Definition
| The pancreas is a rather long organ that lies retroperitoneally along the posterior abdominal wall. Its head is cradled in the C-shaped concavity of the duodenum, and its body and tail extend laterally to the left where it the tail almost reaches the spleen. |
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Term
| What are Islet of Langerhans? |
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Definition
| The bulk of the pancreas is composed of pancreatic exocrine cells and their associated ducts. Embedded within this exocrine tissue are roughly one million small clusters of cells called the Islets of Langerhans, which are the endocrine cells of the pancreas and secrete insulin, glucagon and several other hormones. |
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Term
| What is the structure and function of the pancreatic exocrine cells? |
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Definition
| Pancreatic exocrine cells are arranged in grape-like clusters called acini. The exocrine cells themselves are packed with membrane-bound secretory granules, which contain digestive enzymes that are exocytosed into the lumen of the acinus. Like the granules of gastric chief cells, these are referred to as zymogen* granules because many of the proteins that they secrete are pro-enzymes that must be modified in the intestinal lumen to become active digestive enzymes. Cells that line the ducts produce a watery secretion that is rich in bicarbonate and is important for buffering the chyme as it enters the small intestines from the stomach. |
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Term
| How does the excretions of the exocrine pancreas make its way to the duodenum? |
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Definition
| The lumen of an acinus communicates directly with intercalated ducts, which coalesce into intralobular ducts, which lead to interlobular ducts, and then into the major pancreatic duct. Epithelial cells of the intralobular ducts actually proceed "back" into the lumen of the acinus, where they are called centroacinar cells. The main pancreatic duct fuses with the common bile duct just before its entry into the duodenum. |
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Term
| What are the general characteristics of the liver? |
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Definition
| The liver is the largest gland in the body, and the largest visceral organ (the largest organ being the skin). Weighing approximately 1.5 Kg (3.3 lb), it represents about 2.5% of the total body weight. It receives, metabolizes and stores breakdown products of digestion. The liver is truly an amazing organ. It has over 200 functions that can be divided into three main categories: metabolic regulation, hematological regulation, and bile production. For the purpose of this course, we are gong to cover the general functional anatomy of the liver and associated duct system, and provide a simple overview of how bile flows from the liver to the duodenum. The liver secretes bile, which is emptied into the duodenum and is essential for the digestion and absorption of fats. |
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Term
| Describe the surfaces of the liver |
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Definition
| The upper, diaphragmatic surface of the liver is very smooth. Its posterior surface is deeply grooved to accommodate the inferior vena cava. The lower, visceral, surface of the gallbladder is concave and is directed inferiorly and posteriorly. The gallbladder and porta hepatis are located on this surface. The porta hepatis is the region where vessels and bile ducts enter or leave the liver. |
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Term
| Describe the lobes of the liver |
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Definition
| The liver is anatomically divided by the falciform ligament into the right and left lobes. The quadrate lobe is that part to the right of the falciform ligament and to the left of the gallbladder. The caudate lobe is a small lobe on the posterior aspect of the liver between the lesser omentum and the groove of the inferior vena cava. The right and left halves of the liver are functionally separate, each receiving its own arterial blood supply, bile ducts, portal venous blood supply, and systemic venous drainage. |
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Term
| Describe the arterial and venous supply to the liver |
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Definition
| The liver receives arterial blood from branches of the celiac trunk and venous blood from the GI tract by way of the portal vein. Venous blood exits the liver by way of hepatic veins that drain directly into the inferior vena cava. |
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Term
| Describe the histology of liver lobules |
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Definition
| Histologically, the liver is divided by connective tissue into hundreds of thousands of hexagonally shaped liver lobules that represent the functional units of the liver. Each liver lobule represents a stack of one-cell thick layers of liver cells. The six “corners” of the liver lobule are called portal triads because in this region, hepatic arteries, portal veins and bile ducts can be seen in cross section. In the center of each lobule is a vein called the central vein that drains into the hepatic venous system. |
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Term
| How are hepatocytes arranged? |
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Definition
| hepatocytes are arranged like spokes of a wheel in rows that pass from the central vein to the edge of a lobule. Sinusoids between adjacent plates of hepatocytes carry blood from the branches of the hepatic artery (oxygenated blood) and portal vein (deoxygenated, nutrient-rich blood) to the central vein. |
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Term
| What do sinusoids in the liver contain? |
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Definition
| In addition to typical endothelial cells, the sinusoidal contains phagocytic cells, called stellate cells (also known as Kupffer or reticuloendothelial cells). The stellate cells engulf pathogens, cellular debris and damaged blood cells, and they store iron, lipids and heavy metals that are absorbed by the GI tract. |
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Term
| What are the three primary schemes used to describe the functional units of the liver? |
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Definition
| The classic lobule places the central vein in the center, the portal lobule is triangular in shape, with central veins at each corner, and the portal acinus is oval shaped with central veins at either end, and hepatocytes draining bile towards the middle. The portal acinus seems to be the scheme of choice. |
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Term
| What are hepatocytes responsible for other than their metabolic and hematological functions? |
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Definition
| The constant production and secretion of bile |
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Term
| How much bile does a typical adult produce daily? |
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Definition
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Term
| What are the two stages of bile secretion? |
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Definition
| Initially, hepatocytes secrete bile into canaliculi, from which it flows into bile ducts. This hepatic bile contains large quantities of bile acids, cholesterol and other organic molecules. Then, as bile flows through the bile ducts it is modified by addition of a watery, bicarbonate-rich secretions from ductal epithelial cells. |
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Term
| What is the path of bile flow from the liver? |
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Definition
| Within the hepatic lobules, bile is secreted from the apical ends of hepatocytes into a network of tiny channels, called canaliculi. The canaliculi transport bile from the hepatocytes outward, at right angles to the sinusoids, along the hepatic lobule to bile ductules, which in turn drain into to the bile ducts. The right and left hepatic ducts collect bile from bile ducts in the right and left lobes of the liver, respectively. These ducts converge to form the common hepatic duct. From the common hepatic duct, bile can flow directly into the common bile duct, which merges with the duodenum at the sphincter of Oddi. |
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Term
| What is the sphincter of Oddi? |
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Definition
| Where the common bile duct merges with the duodenum. Between meals, when the tone of the sphincter of Oddi restricts the flow of bile, bile is routed along the cystic duct into the gallbladder. |
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Term
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Definition
| The gallbladder is a pear-shaped, muscular sac that acts to store and concentrate bile between meals. |
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Term
| What are the general histological characteristics of the gallbladder? |
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Definition
| The gallbladder contains absorptive epithelial cells, no muscularis mucosa, and rather thin muscularis externa that is comprised of randomly oriented bundles of smooth muscle. |
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Term
| How is bile concentrated in the gall bladder? |
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Definition
| Typically, bile is concentrated five-fold in the gallbladder by absorption of water and small electrolytes - virtually all of the organic molecules are retained. |
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Term
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Definition
| a solution that promotes the digestion of fats, is produced in the liver, and is transported to the gallbladder |
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Term
| How does bile reach the gallbladder? |
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Definition
| Through the hepatic and cystic ducts |
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Term
| How does bile reach the duodenum from the gallbladder? |
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Definition
| After a meal, the gallbladder contracts, and bile flows through the cystic and common bile ducts, and through the sphincter of Oddi, into the lumen of the duodenum. |
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Term
| What are the three principle mechanisms by which gastrointestinal function is regulated? |
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Definition
| Paracrine, endocrine, and neural |
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Term
| What is paracrine regulation of the GI tract? |
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Definition
| Paracrine regulation describes the process whereby a transmitter is released from a sensing cell (entero-endocrine cells in the intestinal mucosal) that acts via diffusion on neighboring cells. The target tissue must have appropriate receptors for each paracrine agent, which are often peptides. Paracrine agents can exert their actions on several cell types in the gut wall, including other enteroendocrine cells. |
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Term
| What is an example of paracrine regulation in the GI tract? |
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Definition
| An example of a paracrine mechanism in the gastrointestinal tract is the inhibitory action of somatostatin (released by D cells) on gastrin-releasing (G) cells in the gastric antral mucosa. Another important paracrine agent is histamine, which is found in endocrine-like (ECL) cells in the gastric mucosa, some nerves and also in immune cells (mast cells). Yet another, serotonin (5-hydroxytryptamine, 5-HT) is released from specialized enteroendocrine cells called enterochromaffin (EC) cells. Serotonin is important in transmitting information regarding changes occurring in the lumen of the gut to nerves in the gut wall. |
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Term
| What is autocrine regulation of the GI tract? |
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Definition
| Autocrine communication is a form of paracrine regulation that involves feedback onto the cell or set of cells that release that compound. |
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Term
| What produces somatostatin? |
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Definition
| Delta cells (δ-cells or D cells) are somatostatin-producing cells. They can be found in the stomach, intestine and the Islets of Langerhans in the pancreas. |
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Term
| What endocrine regulation of the GI tract? |
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Definition
| Endocrine (hormonal) regulation in the GI tract describes the process whereby enteroendocrine cells respond to a stimulus by releasing signaling molecules that travel via the vasculature to their target cells or tissues. A particular cell or tissue will only respond to the hormone if it possesses high affinity receptors specific for the hormone. There are many examples of endocrine mediated responses in the gastrointestinal tract, including the action of gastrin on the gastric parietal cell, the stimulation of pancreatic secretion by secretin and cholecystokinin (CCK), and the actions of insulin on glucose handling in peripheral tissues. |
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Term
| What are examples of endocrine regulation of the GI tract? |
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Definition
| There are many examples of endocrine mediated responses in the gastrointestinal tract, including the action of gastrin on the gastric parietal cell, the stimulation of pancreatic secretion by secretin and cholecystokinin (CCK), and the actions of insulin on glucose handling in peripheral tissues. |
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Term
| What is a neurocrine response in the GI tract? |
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Definition
| A neurocrine (or neural synaptic) response is mediated by the release of transmitters from nerves onto other neurons, muscle or gland cells. |
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Term
| What are the two sets of nerves in the GI tract? |
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Definition
| The rich innervation of the gastrointestinal tract can be divided into two sets of nerves, extrinsic and intrinsic, on the basis of the locations of the neuronal cell bodies that give rise to the nerve fibers that innervate the gut. Extrinsic innervation is defined as the neural innervation with cell bodies that lie outside of the gut wall; extrinsic nerves are associated with the parasympathetic and sympathetic divisions of the autonomic nervous system. The nerve cell bodies of intrinsic (or enteric) neurons lie within the gut wall. The neurons and their processes, which will be described in greater detail below, comprise the enteric nervous system. |
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Term
| What organs are more dependent on extrinsic innervation in the GI tract? |
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Definition
| the esophagus and stomach are quite dependent on extrinsic “long reflexes” involving the vagus nerves |
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Term
| What reflex in the GI tract involves primarily the activity of the intrinsic nervous system? |
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Definition
| intestinal reflexes, though they can also be modulated by extrinsic output |
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Term
| How can the extrinsic innervation of the GI tract be divided? |
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Definition
| Into the parasympathetic and sympathetic systems |
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Term
| What is the parasympathetic preganglionic innervation portion of the extrinsic innervation of the GI tract? |
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Definition
| The parasympathetic preganglionic innervation of the gut gut is provided by nerves that pass to the gut via the vagus and and pelvic nerves. Cell bodies (preganglionic neurons) lie in the the brainstem or sacral spinal cord and their axons enter the target target organ and synapse with intrinsic neurons (postganglionic neurons). |
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Term
| What does the vagus nerve innervate in the GI tract? |
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Definition
Providing parasympathetics, the vagus nerves innervate ganglia in
ganglia in the esophagus, stomach, gallbladder, pancreas, and the
the first part of intestine, cecum and proximal colon (roughly to
to the left colic flexure). |
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Term
| What do the pelvic nerves innervate in the GI tract? |
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Definition
Providing parasympathetics, the sacral parasympathetic outflow (S2-4)
(S2-4) travels by way of the pelvic nerves and innervates the
descending colon, sigmoid colon and rectum. |
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Term
| What is the principal parasympathetic neurotransmitter? |
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Definition
| The principal parasympathetic neurotransmitter is acetylcholine, and the synapse between the pre- and post-ganglionic neuron is referred referred to as nicotinic, as it involved the action of acetylcholine acetylcholine being mediated by nicotinic receptors. |
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Term
| Do parasympathetic nerves in the GI tract carry afferent or efferent fibers? |
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Definition
| Parasympathetic nerves associated with the gut carry afferent afferent (from the end organ to the CNS) and efferent (from the the CNS to end organ) fibers and are involved in the regulation of regulation of all gut functions. |
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Term
| What is the sympathetic innervation of the GI tract? |
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Definition
| Part of extrinsic innervation, sympathetic innervation of the gut is supplied by nerves with cell bodies in the spinal cord and fibers that terminate in the prevertebral ganglia (celiac, superior and inferior mesenteric ganglion). These are the preganglionic neurons. The postganglionic cell bodies are in the prevertebral ganglia, and the fibers leave the ganglia and innervate intrinsic neurons. |
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Term
| What is the primary neurotransmitter in the sympathetic portion of the extrinsic innervation of the GI tract? |
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Definition
| The neurotransmitter between the pre- and postganglionic neurons is acetylcholine acting at a nicotinic synapse. However, the postganglionic neurons use norepinephrine as the principal neurotransmitter although a number of peptides are co-localized with norepinephrine. |
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Term
| In the GI tract, is sympathetic innervation typically inhibitory or excitatory? |
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Definition
| In general, sympathetic input tends to be inhibitory – ie tends to relax smooth muscle, and inhibit ion and water secretion. A major target of the sympathetic postganglionic nerves that innervate the gut is the intrinsic nerves of the gut. By inhibiting enteric nerves, sympathetic input can down-regulate motility and secretion. |
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Term
| Where are the cell bodies for the parasympathetic and sympathetic sensory (afferent) fibers located? |
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Definition
| The cell bodies are located in nodose and the dorsal root ganglia (sensory ganglia). |
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Term
| What do the sensory (afferent) fibers of parasympathetic and sympathetic nerves in the extrinsic portion of the GI tract do and how do they work? |
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Definition
These fibers innervate and project peripherally to all layers of gut, and terminate in the brainstem and spinal cord. Afferent fibers respond to chemical and mechanical stimulation of the smooth muscle and mucosa. Sensory (afferent) nerves that innervate the gut respond to such stimuli as pH, osmolality, specific chemicals like amino acids or glucose, temperature, temperature, tension and touch. Nerves that are sensitive to pH play a play a particularly crucial role in the the duodenum. Recent studies suggest that enteroendocrine cells transmit paracrine signals from the lumen to to underlying sensory nerve fibers. The vagal afferent innervation
innervation of the gut is primarily involved in regulation of homeostasis (satiety, digestive reflexes) and spinal afferents transmit information related to pain and discomfort. Sacral afferent fibers appear to conduct both homeostatic and nociceptive (pain and discomfort-related) information. |
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Term
| What do the sensory (afferent) fibers of parasympathetic and sympathetic nerves in the extrinsic portion of the GI tract respond to? |
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Definition
| Sensory (afferent) nerves that innervate the gut respond to such stimuli as pH, osmolality, specific chemicals like amino acids or glucose, temperature, temperature, tension and touch. Nerves that are sensitive to pH play a play a particularly crucial role in the the duodenum. |
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Term
| How do the sensory (afferent) fibers of parasympathetic and sympathetic nerves in the extrinsic portion of the GI tract differ with respect to vagal, spinal, and sacral afferent? |
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Definition
The vagal afferent innervation
innervation of the gut is primarily involved in regulation of homeostasis (satiety, digestive reflexes) and spinal afferents transmit information related to pain and discomfort. Sacral afferent fibers appear to conduct both homeostatic and nociceptive (pain and discomfort-related) information. |
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Term
| What types of activity does the enteric nervous system allow for? |
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Definition
| Secretory, motility, and vasodilatory reflexes can be generated within the confines of the bowel because the enteric nervous system (ENS) contains all of the elements of a reflex circuit. The enteric nervous system can perform integrative functions that are independent of the central nervous system, but it also communicates with the "big brain" via the sympathetic and parasympathetic nerves. Thus, this nervous system is often called the "little brain in the gut" or the ‘second brain’. |
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Term
| How are the plexuses of the enteric NS linked? |
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Definition
| the submucosal and myenteric plexuses of the enteric nervous system contain primary afferent neurons, interneurons, excitatory motor neurons and inhibitory motor neurons. Interganglionic fiber tracts link neurons in the two plexuses, and extrinsic nerves can modulate actions of both plexuses. |
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Term
| What are "brain-gut peptides"? |
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Definition
| a large number of neurotransmitters that are peptides are present both in enteric neurons and in the brain, and were first discovered in the gut. For this reason, these are known as "brain-gut peptides". |
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Term
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Definition
| Because the enteric nervous system houses intrinsic reflex circuitry, it is unique in that the gut contains primary afferent (sensory) neurons (called intrinsic primary afferent neurons = IPANs). These afferent neurons are involved in mediating neural reflexes in the wall of the gut. They respond to many of the same stimuli as the extrinsic afferent neurons, including mechanical and chemical stimuli. |
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Term
| Are there more neurons in the gut or the spinal cord? |
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Definition
| >100 million more in the gut |
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Term
| Is the ultrastructure of the enteric NS more like the central or peripheral NS? |
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Definition
| The ultrastructure of the enteric nervous system is more like that of the central nervous system than the peripheral nervous system. It consists of a very tightly packed neurophil, and unmyelinated axons are bare rather than being surrounded by a glial sheath. |
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Term
| How are glia of the enteric NS compared to those in the central NS? |
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Definition
| Glia of the enteric nervous system are very similar to astrocytes found in the central nervous system. Like astrocytes, enteric glial cells produce Glial Fibrillary Acidic Protein. They can also produce interleukins and they express MHC class II antigens in response to stimulation by cytokines. In the absence of enteric glia, which occurs in GFAP knockout mice, widespread enteritis (intestinal inflammation) occurs. |
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Term
| How does serotonin affect gut neural reflexes? |
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Definition
| Essentially all intrinsic and extrinsic gut reflexes (ie, peristalsis, secretion, vasodilation, pain and discomfort, vomiting) can be elicited by the release of serotonin (5-hydroxytryptamine; 5-HT) from a special subclass of enteroendocrine cells called enterochromaffin (EC) cells. EC cells have been identified as sensory transducers that respond to luminal stimuli by secreting serotonin. Serotonin released from EC cells acts on intrinsic (enteric) and extrinsic (vagal) afferent fibers to initiate reflex responses. |
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Term
| What are EC cells in the gut? |
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Definition
| Serotonin (5-hydroxytryptamine; 5-HT) is released from a special subclass of enteroendocrine cells called enterochromaffin (EC) cells. EC cells have been identified as sensory transducers that respond to luminal stimuli by secreting serotonin. Serotonin released from EC cells acts on intrinsic (enteric) and extrinsic (vagal) afferent fibers to initiate reflex responses. |
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Term
| What are the two ways 5-HT can act within the bowel? |
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Definition
| 5-HT released from EC cells acts as a paracrine substance and 5-HT released from neurons acts as a neurotransmitter. |
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Term
| When released from EC cellls what receptors will 5-HT stimulate? |
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Definition
| When released from EC cells, 5-HT stimulates 5-HT3 receptors on vagal and spinal (extrinsic) afferent fibers as well as 5-HT3 and 5-HT4 receptors on enteric (intrinsic) afferent fibers. |
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Term
| What happens if 5-HT3 and 5-HT4 receptors are blocked? |
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Definition
| Blockade of 5-HT3 and 5-HT4 receptors with receptor-specific antagonists eliminates peristalsis. |
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Term
| What, other than intestinal secretion and peristalsis, can 5-HT initiate? |
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Definition
| 5-HT released from EC cells can initiate responses such as nausea and vomiting |
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Term
| How is the action of 5-HT terminated? |
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Definition
| The actions of 5-HT in the gut are terminated by reuptake involving the same serotoninselective reuptake transporter (SERT) that works on serotonin in the brain and is the target of serotonin-selective reuptake transporters (SSRIs) such as Prozac. |
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Term
| What are antagonists of 5-HT3 currently being used for? |
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Definition
| 5-HT3 receptor antagonists (Alosetron, Granisetron Tropisetron and Ondansetron) appear to reduce visceral sensitivity and have inhibitory effects on colonic motor activity. Clinical studies suggest that these agents may have a role in painful, diarrhea-predominant irritable bowel syndrome. |
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Term
| What are agonists of 5-HT4 currently being used for? |
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Definition
| 5-HT4 agonists (tegaserod, sold as Zelnorm) had been approved as a prescription drug to treat constipation-predominant IBS. It facilitates colonic peristalsis and thereby reduces abdominal pain. Gastrointestinal prokinetics that act as 5-HT4 agonists, have been widely used for the management of functional gut disorders. |
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Term
| What are some of the problems associated with agonists of 5-HT4 receptors? |
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Definition
| Recently, cisapride (a partial 5-HT4 receptor agonist) was pulled from the market because it can induce dose-dependent cardiac adverse effects, including lengthening of the electrocardiographic QT interval, syncopal episodes and ventricular dysrhythmias. This is side-effect of cisapride involves the blockade of distinct voltage-dependent K+ channels (hERG channels), thus delaying cardiac repolarization and prolonging the QT interval. hERG channels have now been identified in gastrointestinal smooth muscle, and it is possible that a component of the prokinetic effect of cisapride is due to suppression of these channels leading to a depolarization and increased excitability. Because of this experience with cisapride, all drugs that are submitted for FDA approval must be tested to determine whether they alter hERG channel function. |
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Term
| What is the general structure of the endocrine system of the gut? |
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Definition
| The gastrointestinal tract is the largest endocrine organ in the body. Hormones are released from endocrine cells (enteroendocrine cells) that are located in mucosal lining of gut from the stomach to the rectum. These cells extend from the lumen to the basement membrane. The luminal (apical) membranes have receptors for chemical components of chyme, and, if conditions are appropriate, enteroendocrine cells release signaling molecules into the lamina propria from basal membrane. Those that enter the blood stream and have distant actions are considered to act as hormones. |
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Term
| What types of signaling molecules are GI hormones? |
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Definition
| All gut hormones are polypeptides. Like other hormones, GI hormones are delivered to their targets throughout the body by the vascular system and they act on cells that contain appropriate receptors for that hormone. Typically, hormones have a very high affinity for their receptors and therefore can activate them at very low concentrations (ie. picomolar to low nanomolar range whereas classical transmitters such as acetylcholine and \norepinephrine work in the micromolar range). |
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Term
| To be considered a GI hormone a peptide MUST ... |
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Definition
| To be considered a GI hormone, the peptide (1) must be shown to be present in the gut, (2) must be synthesized by an endocrine cell in the gut, (3) the structure must have been identified, (3) it must be released by an appropriate physiological stimulus, (4) it must produce an appropriate physiological effect when infused exogenously at the appropriate blood level, and (5) it actions are blocked by appropriate antagonists or antisera. |
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Term
| What are the widely accepted GI hormones? |
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Definition
| gastrin, cholecystokinin, secretin, gastric inhibitory peptide (GIP; also known as glucose-dependent insulinotrophic peptide), and motilin |
|
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Term
| What are the effects of CCK on gastric and biliary motility? |
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Definition
Fats and protein cause CCK release from I cells
CCK enters the circulation, reaches the gallbladder and increases gallbladder tone CCK activates local neural circuits between the duodenum and the sphincter of Oddi that decrease sphincter tone CCK and distension activate vagal afferent fibers that initate vagal reflexes to increase gallbladder tone, decrease fundus tone, and decrease antral contractile activity The net result is decreased gastric emptying and increased bile flow. |
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Term
| What is the role of CCK in intestinal feedback? |
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Definition
| CCK is released from endocrine cells in the duodenal mucosa in response to nutrients. CCK is physiologically important in the regulation of gastric emptying, gallbladder contraction, relaxation of Sphincter of Oddi and pancreatic secretion. In addition, recent experimental evidence suggests that CCK may not act as a hormone to inhibit gastric emptying; rather, it stimulates vagal afferent fiber discharge to produce a vago-vagal reflex decrease in gastric emptying (increased proximal stomach compliance and decreased contractile activity in the antrum). |
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Term
| What is the role of CCK in bile flow? |
|
Definition
| In response to food in the duodenal lumen, CCK is secreted from enteroendocrine cells into the lamina propria where it acts on intrinsic and extrinsic primary afferent fibers and enters the blood steam. CCK acts as a paracrine to increase vagal reflexes that cause gallbladder contraction and pancreatic secretion, and to activate intrinsic reflex circuits between the duodenum and the sphincter of Oddi that relax the sphincter. CCK also acts hormonally in gallbladder ganglia to presynaptically facilitate vagal input to gallbladder neurons, and on gallbladder smooth muscle to cause the gallbladder to contract. The net result is gallbladder contraction and decreased resistance to bile flow at the sphincter of Oddi, and ultimately an increase in bile flow. |
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Term
| How do Brunner's glands function? |
|
Definition
| In the submucosal layer of duodenum there are mucus glands called Brunner’s glands. These are compound mucus glands. They respond rapidly to the presence of acid in the first segment of the duodenum by secreting a large amount of alkaline mucus. Vagal stimulation, which occurs while eating, causes these cells to secrete during the Gastric Phase, so this area of the duodenum is primed for the entry of chyme. One of the reasons why this area is particularly susceptible to ulceration is that secretion from Brunners glands is inhibited by the sympathetic nervous system. This action may contribute to stress induced ulceration of this area, as the natural mucus protection is lost. |
|
|
Term
| What GI phase accounts for 90% of pancreatic secretions? |
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Definition
| Duodenal, as food moves from the stomach into the duodenum. |
|
|
Term
| What is the inorganic composition of pancreatic secretions? |
|
Definition
| Inorganic secretions of the pancreas include water and ions (predominately bicarbonate, Na+, K+, Cl-). Only HCO3 - and Cl- concentrations change significantly with flow rate. Acinar secretions are high in Cl- but low in volume. Ductal secretions are high in volume and high in HCO3-. This secretion of aqueous bicarbonate solution washes the enzymes from the pancreas into the duodenum, so the greatest enzyme secretion occurs when there is also bicarbonate secretion. |
|
|
Term
| What enzyme is responsible for activating pancreatic enzymes in the duodenal lumen? |
|
Definition
| Enteropeptidase, formerly known as enterokinase |
|
|
Term
| What are the primary ways that pancreatic exocrine secretion in the duodenal phase is regulated? |
|
Definition
| High H+ stimulates secretin release; nutrients cause CCK release, and neural flexes (extrinsic) also stimulate secretions. |
|
|
Term
| How do neural reflexes stimulate pancreatic secretion? |
|
Definition
| The presence of nutrients, acid, etc., in the duodenal lumen stimulates afferent fiber discharge, which stimulates pancreatic secretion via vago-vagal (vagal afferent-vagal efferent) reflexes. These reflexes are activated, at least in part, by the release of CCK and 5-HT from enteroendocrine cells onto vagal afferents in the duodenal lamina propria. These reflexes are also activated during the cephalic and gastric phases. |
|
|
Term
| Why doesn't the pancreas digest itself? |
|
Definition
• Enzymes that attack membranes (eg trypsin) are synthesized as inactive precursors
• Enzymes that do not attack membranes secreted as active forms (eg lipase)
• Enzymes are segregated within membrane-bound compartments
• Pancreatic acinar cells contain intracellular trypsin inhibitor
• The activating enzyme, enteropeptidase, is geographically separated from pancreas |
|
|
Term
| What are the two motility patterns in the small intestine? |
|
Definition
| Postprandial and interprandial |
|
|
Term
| What is postprandial motility? |
|
Definition
| Postprandially (following a meal), when the lumen of the small intestine contains chyme, two types of motility predominate: segmentation contractions chop, mix and roll the chyme, and peristalsis slowly propels it toward the large intestine. |
|
|
Term
| What is interprandial motility? |
|
Definition
| The interdigestive state is seen between meals, when the lumen is largely devoid of contents. During such times, so-called housekeeping contractions propagate from the stomach through the entire small intestine, sweeping it clear of debris. This complex pattern of motility is also known as the migrating motor complex and is the cause of the "growling" sounds that emanate from our abdomen at the most inopportune times. |
|
|
Term
| What is the motility of the small intestine regulated by primarily? |
|
Definition
| The enteric nervous system, although these local nervous signals are modulated by inputs from the CNS and a number of gastrointestinal hormones that appear to affect motility. |
|
|
Term
|
Definition
| When the stomach is empty a motor event called the migrating motor complex (MMC) is initiated every 90 minutes or so. These are followed by periods of quiescence. The function is to propel residual contents left in the stomach and intestine into colon. These cycles of motor activity are interrupted by feeding, an effect dependent on the extrinsic innervation. MMCs are thought to be activated by the secretion of the peptide, motilin. It is still not conclusively proven that motilin causes the MMC, but its secretion coincides with the motor complex and occurs at about the same frequency in the fasting state, and eating inhibits its release. During a migrating contraction, there are intense electrical and contractile events that progress from the stomach along the gut to the distal colon. |
|
|
Term
| What is intestinal psuedoobstruction? |
|
Definition
| Contractile activity occurs continuously in a dysregulated manner |
|
|
Term
|
Definition
| Marked decrease or absence of contractile activity that can result from irritation of the peritoneum during surgery, peritonitis, and also results from electrolyte abnormalities, medication side effects, and in association with pancreatitis. |
|
|
Term
| What is a power propulsion? |
|
Definition
| an intestinal motor pattern that is specialized for rapid propulsion over long distances. Power propulsion is a protective response to harmful agents. As a motility pattern power propulsion it is reflected as strong, long-lasting contractions of the circular muscle that propagate for extended distances along the small and large intestine. These giant migrating contractions are considerably stronger than the phasic contractions during the MMC or fed pattern. Giant migrating contractions last 18-20 seconds and span several cycles of the electrical slow waves. They are a component of a highly efficient propulsive mechanism that rapidly strips the lumen clean as it travels at about 1 cm/sec over long lengths of intestine. Power propulsions can occur retrograde during vomiting. |
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Term
| What are the two processes that establish an osmotic gradient that pulls water into the lumen of the intestine? |
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Definition
| Increases in luminal osmotic pressure resulting from influx and digestion of foodstuffs, including starch, etc. Also, crypt cells actively secrete electrolytes, leading to water secretion. |
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Term
| What ion is responsible for the majority of intestinal water secretion? |
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Definition
| Cl-. Na+ follows Cl- into the lumen, creating the osmotic gradient for water flow into the lumen |
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Term
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Definition
| CFTR is a cyclic AMP-dependent chloride channel. The channel is responsible for secretion of water in many types of epithelial cells, including duct cells in the exocrine pancreas. |
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Term
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Definition
| Released from the mucosa by the presence of chyme, this enzyme converts trypsinogen (released from the pancreatic acinar cells) to trypsin. Trypsin in turn converts other pancreatic enzymes to active forms. Enteropeptidase is a brush border enzyme that is anchored by a transmembrane stalk to the enterocytes that make up the brush border. Thus, brush border enzymes remain in place and are not swept along with the chyme. |
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Term
| How is mucus secretion by goblet cells elicited? |
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Definition
| Primarily by irritating stimuli rather than in response to hormones or other secretogogues. |
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Term
| What are the two types of pathways for goblet cell secretion? |
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Definition
• Constitutive or basal secretion: low level, unregulated and essentially continuous secretion. This pathway is dependent on cytoskeletal movement of secretory granules.
• Stimulated secretion: regulated exocytosis of granules in response to extracellular stimuli. This pathway provides an ability to dramatically increase mucus secretion |
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Term
| What is the vomiting reflex? |
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Definition
| The vomiting reflex involves both somatic and autonomic neural pathways. Output from the vomiting center in the brainstem causes contraction of intercostals and abdominal muscles, and fixation of the diaphragm to prevent inspiration. Reverse peristalsis in the upper jejunum, duodenum and stomach drives a wave of chyme towards the proximal stomach. Relaxation of the lower and upper esophageal sphincters and the pharynx, combined with the elevated pressure in the gastric lumen propels the chyme through the oral, and sometimes nasal cavities. |
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Term
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Definition
| Regurgitation is a motor pattern distinct from vomiting. It is the ejection of previously swallowed material from the esophagus or pharynx (rarely the stomach) and usually occurs due changes in intrathoracic or intra-abdominal pressure. Although regurgitation shares some similarities with vomiting, it is not preceded by many of the behavioral signs that precede vomiting, and, in general, does not involve contractions of the inspiratory muscles or repetitive contractions of the abdominal muscles. |
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Term
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Definition
| Gut-associated lymphoid tissue. Includes Peyer's patches, limna propria lymphocytes (IgA secreting B cells), and intraepithelial lymphocytes found in the basolateral spaces between luminal epithelial cells. |
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Term
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Definition
| Microfold cells. M cells are typically situated over lymphoid follicles and they endocytose a variety of protein and peptide antigens. Instead of digesting these proteins, M cells transport them into the underlying tissue, where they are taken up by macrophages. |
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Term
| What regions of the colon are responsible for absorption of water and ions? |
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Definition
| The cecum and ascending colon |
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Term
| What is the stimuli for the colonic phase? |
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Definition
| Mechanical stimulation occurs by rectal distension, and chemical stimulation by the presence of free fatty acids in the lumen. |
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Term
| What are the pathways responsible for the colonic phase effectors occurring? |
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Definition
| Both extrinsic and intrinsic neural pathways. Also some evidence that there is a hormonal role for peptide YY |
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Term
| What changes in function (effectors) are associated with the colonic phase? |
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Definition
• propulsive motor patterns to enhance motility,
• inhibition of secretion and motor function of proximal GI tract,
• absorption of water and ions. |
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Term
| What three patterns of motility are seen in the colon? |
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Definition
| Segmentation, antiperistaltic contractions, and mass movements |
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Term
| What are antiperistaltic contractions in the colon? |
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Definition
| Propagate towards the ileum, serving to retard the movement of luminal contetns through the colon and allowing additional opportunity for absorption of water and electrolytes. |
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Term
| What is mass movement in the colon? |
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Definition
| Mass movements constitute a type of motility not seen elsewhere in the digestive tube. Known also as giant migrating contractions, this pattern of motility is like a very intense and prolonged peristaltic contraction which strips an area of large intestine clear of contents. |
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Term
| What two reflexes following a meal are responsible for increased colonic motility? |
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Definition
| Gastrocolic and duodenol colic, both manifestations of enteric nervous system control. Also, distension of the colon is another stimulus for contractions. |
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Term
| What are the two major pathophysiologic mechanisms for diarrhea? |
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Definition
| Decreased absorption of fluid and electrolytes (osmotic), or increased secretion of fluid and electrolytes (secretion) |
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Term
| What are the causes of osmotic diarrhea? |
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Definition
| It can be caused by the presence of excessive amounts of poorly absorbed solutes, by maldigestion of normal amounts of solutes, or malabsorption of normal amounts of solutes. In any of these cases, the increased osmotic pressure in the gut lumen draws water across the intestinal epithelium from capillaries and lymph vessels. Overeating or sudden change to a new diet can cause osmotic diarrhea because of the large amounts of unabsorbed food that sits in the lumen until digestive enzyme levels can adapt to the presence of new or overabundant luminal substrates. |
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Term
| What conditions can reduce food digestion and absorption leading to osmotic diarrhea? |
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Definition
• Reduced output of enzymes and other substances that aid digesting, including bile, pancreatic and brush border enzymes.
• Atrophy of the intestinal mucosa, as occurs in celiac disease, which decreases levels of brush border enzymes and decreases surface area for absorption
• Colonic osmotic diarrhea can occur if unabsorbed food enters the colon. Once in the colon, they induce water flow and paracellular loss of electrolytes into the lumen (due to solvent drag). Unabsorbed food can also be fermented by colonic bacteria, producing gas and higher numbers of osmotically active particles that may not be absorbed. |
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Term
| What are the causes of secretory diarrhea? |
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Definition
| Many infectious agents can cause secretory diarrhea including the bacteria Vibrio cholerae, enterotoxigenic E. coli, Salmonella, Yersinia, and Campylobacter. A variety of endogenous, abnormal conditions also cause secretory diarrhea because they release excessive amounts of chemical transmitters that can evoke intestinal secretion. |
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Term
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Definition
| The normal set-point for body isotonic Na-saline stores is by definition, euvolemia, which is just the right amount of isotonic Na-saline in the ECF to ensure blood pressures high enough to provide optimal cardiovascular output and tissue perfusion, but low enough to prevent damage to blood vessels. The steady state of euvolemia is maintained by physiology that regulates body Na-saline stores so that the daily rate (mmoles/day) of saline excretion equals the daily rate of Na-saline intake. |
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Term
| How is the optimal size of the ECF determined? |
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Definition
| The optimal size of the ECF is determined as the volume at which a healthy cardiovascular system (i.e., heart, blood vessels) can best provide the circulatory needs of body tissues. A lower volume would reduce either the flow or the physiological reserves, while a higher volume would unnecessarily increase pressures, placing an additional load on the system. Any deviation from this optimal set-point for the ECF is itself the signal that regulates the volume of the ECF! This point, which is generally under-appreciated, is a central key concept. |
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Term
| What is the signal that regulates the volume of the ECF? |
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Definition
| Any deviation from the optimal set-point for the ECF is itself the signal that regulates the volume of the ECF. |
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Term
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Definition
| Any drug that inhibits a Na+ resabsorption step along the kidney nephron |
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Term
| What would be the effect of adding a liter of half-normal saline (0.45%) NaCl to the body? |
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Definition
| A liter of half-normal saline (0.45%) NaCl contains 500-mL of isotonic saline and 500-mL of solute-free water. If added to the body, the ECF would be expanded by the 500-mL of isotonic Na-saline while the 500-mL of solute-free water would distribute with 2/3 going to the ICF and 1/3 going to the ECF. In the end, the ECF would gain 667-mL (500-mL of isotonic saline and 167-mL of solute-free water) and the ICF would gain 333-mL of solute-free water. |
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Term
| In essence what is a "clinical volume status"? |
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Definition
| A measure of the volume of the ECF |
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Term
| How can clinical volume status be measured? |
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Definition
| The clinical volume status is determined non-invasively by physical examination. Extensions of this exam may include ultrasonic or plethesmographic studies of the central vessels, or may involve modestly invasive procedures such as monitoring of central pressures via catheter. Although some laboratory studies (e.g., fractional excretion of Na) may help support the clinical assessment of volume status, they should not be used instead of a careful physical examination. |
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Term
| What is the problem in inviduals with clinical hypovolemia? |
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Definition
| • Clinically hypovolemic individuals are those who are depleted of isotonic Na-saline and their ECF is contracted. Unless that is the intention of therapy, their body Na-saline stores should be repleted with isotonic Na-saline to re-expand their ECF. |
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Term
| What is the problem in inviduals with clinical hypervolemia? |
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Definition
| • Clinically hypervolemic individuals are those who are carrying excess isotonic Na-saline and their ECF is expanded. These people usually have organ dysfunction (e.g., congestive heart failure, renal disease, or cirrhotic liver disease). In general, and especially if they have edema, they should be treated with sodium restriction and natriuretic agents to remove Na-saline from the ECF. The goal of therapy is to get them into a new steady state by gradually lowering their ECF volume as close to euvolemic as their physiology will allow. |
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Term
| How is euvolemia maintained day after day, no matter what we eat and how much we eat? |
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Definition
| Any deviation from the optimal set-point for the ECF is itself the signal that regulates the volume of the ECF. During the course of everyday life, there are constant salt and water losses. As will be discussed when we consider body tonicity, the loss of free water will increase tonicity and stimulate thirst. Acting on thirst is a high priority, so free water losses are promptly repleted. Unlike free water, the loss of small amounts of isotonic Na-saline may not be consciously sensed. However, it is physiologically sensed and feedback loops are activated. |
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Term
| ECF volume loss results in what neurohormonal signals? |
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Definition
| Decreased cardiac output, decreased secretion of natriuretic peptides due to the decreased stretch of the atria, leading to decreased urinary output; and activation of the renin-angiotensin II aldosterone system to increase Na+ reabsorption by the kidney. |
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Term
| ECF volume increase is common in today's society. How does the body combat ECF increase? |
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Definition
| Increased cardiac output, increased secretion of natriuretic peptides due to the increased stretch of the atria, leading to increased urinary output; and deactivation of the renin-angiotensin II aldosterone system to increase Na+ reabsorption by the kidney. |
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Term
| How is the nephron able to sense and regulate its own flow of urine formation? |
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Definition
| The early part of the distal tubule of every nephron comes back to the vascular pole (between the afferent and efferent arteriole) of the glomerulus – providing a sensing and control mechanism for regulating its filtration rate. |
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Term
| What is the glomerular basement membrane and what does it do? |
|
Definition
| The GBM is the unique capillary basement membrane separating the capillaries from the tubule lumen. This basement membrane is thicker than in other capillaries, and has a unique epithelial cell on the urine side, called a podocyte. Each podocyte has many foot processes (pedicels) that imbed themselves in the membrane. The GBM and the epithelial foot processes are the main barriers to filtration of large molecules. |
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Term
| What is a mesangial cell? |
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Definition
| Mesangial cells have contractile elements that can increase or decrease the size of the capillary loops, and thus limit filtration. They also secrete the collagen that forms the GBM. |
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Term
| What are the layers of the GBM? |
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Definition
| The GBM has a dense midportion (the lamina densa) sandwiched between two less dense portions (the lamina rara externa and interna). Between the pedicels is a black line with a central dot, called the slit diaphragm. |
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Term
| What is the slit diagram? |
|
Definition
| The slit diaphragm is actually made up of interlocking molecules of a recently discovered anchoring protein called nephrin that attaches to the cell membranes of adjacent pedicels, providing 4 x 14 nm slits for passage of molecules. The anchoring portion of nephrin interacts with key cytoplasmic signaling proteins, including podocin, CD2AP and ZO-1. The slits formed by the non-interlocking parts of adjacent nephrin molecules are the primary barrier to filtration of macromolecules. Loss of nephrin leads to heavy proteinuria. |
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Term
| Loss of nephrin leads to … |
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Definition
|
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Term
|
Definition
| Contained in the GBM and pedicels, negatively charged sialoproteins impede the filtration of molecules with a net negative charge that are at or near the size of the slit pores. Albumin is a key negatively charged molecule whose filtration is impeded by charge as well as by size. |
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Term
| How does the kidney filter by charge as well as size? |
|
Definition
| Contained in the GBM and pedicels, negatively charged sialoproteins impede the filtration of molecules with a net negative charge that are at or near the size of the slit pores. Albumin is a key negatively charged molecule whose filtration is impeded by charge as well as by size. |
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Term
| How are kidney tubules divided? |
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Definition
| The tubule is divided into a proximal portion (proximal convoluted and straight tubules), the loop of Henle (with its descending limb, and its thin and thick ascending limb), the distal tubule and collecting duct. |
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Term
| What is the promixal tubule and what does it do? |
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Definition
| The proximal tubule is a high energy high capacity, only partially selective, part of the nephron where approximately 2/3 of the filtered salt and water is reabsorbed. It is the major site of oxygen consumption in the kidney, which is consumed primarily to effect active transport of solute from the urine back into the blood. |
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Term
| What do the thin descending and ascending portions of the loop serve to achieve? |
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Definition
| The thin descending and ascending portions of the loop serve the process of urine concentration but have no active transport capacity. |
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Term
| What does the thick ascending portion of the loop do? |
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Definition
| The thick ascending limb contains key active transport systems that remove solute without water. These transport processes are critical for both urine concentration and dilution. |
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Term
| What do the distal tubule and collecting duct accomplish? |
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Definition
| The distal tubule and collecting duct have transport proteins that involved in the “fine tuning” of the urine, allowing for exquisite electrolyte and fluid balance to occur. |
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Term
| What is the general cell structure of the proximal convoluted tubule? |
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Definition
| The proximal convoluted tubule cell is characterized by a highly convoluted luminal membrane, the so-called “brush border”, increasing dramatically the surface area for fluid and solute reabsorption. It also contains many mitochondria, the engines of oxidative metabolism. |
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Term
| What is the general cell structure of the thin limbs of Henle's loop? |
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Definition
| The cells in the thin limbs of Henle’s loop are simple with few mitochondria |
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Term
| What is the general cell structure of the thick limbs of Henle's loop? |
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Definition
| Complex cells with many mitochondria |
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Term
| What are the two major cell types in collecting tubules? |
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Definition
| Intercalated and principal cells |
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Term
| What are principal cells in collecting ducts responsible for? |
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Definition
| principal cells are devoted to Na+ and water reabsorption and K+ secretion |
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Term
| What are intercalated cells in collecting ducts responsible for? |
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Definition
| intercalated cells are devoted to H+ (or more rarely, to HCO3- ) secretion, and to K+ reabsorption |
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Term
| What is the cell type found in the final portion of the collecting duct (medullary collecting duct)? |
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Definition
| Special cell type is involved in Na+, water and urea reabsorption, H+ secretion and K+ secretion. These powerful cells can reduce the urine sodium and HCO3- concentration to zero, and can increase the K+ concentration in the urine to >15 times the plasma concentration. |
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Term
| What are primary active solute transporters? |
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Definition
| These transport specific solutes across cell membranes against their electrochemical gradient, using energy from the breakdown of ATP. An example is the ubiquitous Na+/K+ ATPase. |
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Term
| What are secondary active solute trasnporters? |
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Definition
| These link the transport of 2 or more solutes, so that one of them, moving down its electrochemical gradient, will carry another with it. The function of these transporters is dependent on the action of the Na+/K+ ATPase to generate the appropriate gradients. Examples are the Na+/H+ exchanger, and the Na+/glucose cotransporter. |
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Term
| What are the general characteristics of the proximal tubule? |
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Definition
| The proximal tubule has a huge surface area for reabsorption and secretion on the urine side of the epithelium, created by the microvilli (the so-called brush border – see figure in the structure lecture). The proximal tubule is metabolically active and recaptures two-thirds of the filtered Na+ and water, all the filtered glucose, and 80% of the filtered HCO3-. Low-molecular-weight proteins crossing the glomerular basement membrane are also reabsorbed here. |
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Term
| How do the key trasnports work together in the proximal tubule? |
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Definition
| The energy for solute transport is generated by the basolateral Na+/K+ ATPase which continually lowers the [Na+] in the cell, allowing for Na+ to enter through the apical membrane. Na+ entry is linked to H+ secretion on NHE3 and to glucose entry on SGLT2. As a result Na+ reabsorption produces H+ secretion against it electrochemical gradient, and glucose entry against its concentration gradient. As solute is reabsorbed, water follows across its pore, aquaporin 1 (AQP1), which is always present in the membrane. |
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Term
| What are the general characteristics of the loop of Henle? |
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Definition
| The loop of Henle is essential for urine concentration and dilution , and its structure and function fit with this role. The loop descends from the cortex into the medulla and then, after a “hairpin” turn, returns to the renal cortex. The descending limb contains AQP1 and is freely permeable to water, but has no solute transporters. The ascending limb, by contrast, contains no aquaporin, but has major solute transport mechanisms, particularly in the thick ascending limb. |
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Term
| How does the ascending differ from the descending limb? |
|
Definition
| The descending limb contains AQP1 and is freely permeable to water, but has no solute transporters. The ascending limb, by contrast, contains no aquaporin, but has major solute transport mechanisms, particularly in the thick ascending limb. This architecture allows for extensive water reabsorption without solute in the descending limb and for extensive solute reabsorption without water in the ascending limb. Separation of solute uptake from water reabsorption is the initiating step for urine concentration and lowers the solute concentration in the urine entering the distal tubule. |
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Term
| What are the key trasnporters in the thick ascending limb? |
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Definition
| The Na+/K+/2 Cl- cotransporter (named NKCC1 or BSC2) is unique to this segment of the tubule. The transporter resides on the apical membrane of epithelial cells, and depends on the basolateral Na+/K+ ATPase to create the gradient that carries Na+ into the cell. Na+, however, can only enter accompanied by a K+ and 2 Cl- ions. Cl- exits the basolateral membrane by an ion channel (CLC5), accomplishing NaCl reabsorption, and K+ recycles partly via a specific K+ channel, called ROMK, on the apical membrane. NKCC1 is responsible for ~ 15% of Na+ reabsorption by the kidney, and is inhibited by a potent class of diuretics called “loop” diuretics. These include furosemide and bumetanide. Function of this transporter is a requirement for the countercurrent system to operate. Blockade by drugs blocks both urine concentration and dilution. |
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Term
| What are the three key components of the countercurrent system? |
|
Definition
1. The countercurrent multiplier – fueled by secondary active transport in the thick ascending limb cells
2. The countercurrent exchanger – a result of the unique vascular architecture (vasa recta) that facilitates solute exchange between descending and ascending limbs.
3. The collecting duct with regulated water and urea reabsorption. |
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Term
| What happens to urine concentration when medullary blood flow is increased? |
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Definition
| Increasing medullary blood flow will limit urine concentrating ability even when ADH is present, because the increase in renal blood flow will tend to wash out the high solute levels in the medulla. |
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Term
| What are the properties of the distal tubule? |
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Definition
| The distal tubule begins as the loop segment returns to its own glomerulus and continues until it joins another distal tubule to form a collecting duct. The early portion of this segment (also known as the distal convoluted tubule) also has a unique transporter, the Na+/Cl- cotransporter, on the apical membrance of its epithelial cells and has no aquaporin. The Na+/Cl- cotransporter is inhibited by the thiazide group of diuretics and normally accounts for 2-5% of Na+ reabsorption. Again the basolateral Na+/K+ ATPase provides the driving force for Na+ uptake. The later portions of the distal tubule merge their characteristics with the collecting duct |
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|
Term
| What are the general properties of the collecting duct? |
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Definition
| The collecting duct begins at the convergence of two or more distal tubules and descends from the renal cortex to the renal pelvis at the tip of the renal pyramids. The collecting duct normally reabsorbs about 2% of the filtered Na+, but its reabsorption at this site is highly regulated. It is also responsible for the acid excretion that lowers urine pH below that of plasma. This segment is unique in that it contains two distinct cell types (the principal cells and the intercalated cells) that have very different transport functions. The principal cells reabsorb Na+ via a unique Na+ channel called ENaC, and secrete K+. |
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Term
| How is Na+ regulation in the collection duct regulated? |
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Definition
| Na+ reabsorption by the principal cell is regulated by aldosterone. This hormone binds to an intracellular receptor and stimulates both ENaC and the Na+/K+ ATPase. |
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Term
| Where can AQP2 be found and what is it? |
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Definition
| AQP2 moves in and out of the membrane under the regulation of ADH. In the absence of ADH, no water channels are in the membrane, and the tubule is virtually impermeant to water. In the presence of ADH (binding to its receptor, called the V2 receptor), AQP2 is inserted into the apical membrane allowing water reabsorption. |
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|
Term
| How do the intercalated cells of the collecting duct function? |
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Definition
| The intercalated cells secrete H+ via an active transporter, the H+ ATPase, or HCO3-, and reabsorb K+ in states of K+ depletion via another active transporter, the H+/K+ ATPase. Most intercalated cells in humans actively secreting H+ into the tubule lumen and moving HCO3- back into the blood. When there is excess HCO3- in the body, however, intercalated cells with a reverse transport polarity, i.e., a Cl-/HCO3- exchanger on the tubule lumen side and a H+ -ATPase on the peritubular capillary side become active. Thus these cells secrete HCO3- into the lumen in a process linked to Cl- reabsorption |
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|
Term
| What are the properties of the inner medullary collecting duct? |
|
Definition
| The collecting duct cells in the inner medullary region of the kidney, near the tip of the renal papillary, are capable of generating huge concentration gradients for Na+, H+, and other substances in the final urine. Strikingly these gradients are achieved by a cell that has neither the characteristics of principal or intercalated cells, but seems to contain the transporters contained in both types of cells. |
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Term
| How is acid produced and balanced in the body (in general)? |
|
Definition
| Each day, the body produces over 15 Mols of acid (H+) through metabolism. The vast majority is the volatile weak acid H2CO3, which exists in equilibrium with CO2, and thus is easily excreted by the lungs. Only 40-80 mols of acid is produced each day that cannot be excreted by the lungs, primarily as a result of the metabolism of sulfur-containing amino acids. This acid reacts with bicarbonate, forming CO2 and the HCO3- consumed in this buffering reaction is eventually replaced by the kidney. |
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|
Term
| What is the major buffer of acid in the human body? |
|
Definition
|
|
Term
| How is the Henderson equation related to CO2? |
|
Definition
The Henderson equation illustrates that [H+] is controlled by adjustments in [H2CO3] and [HCO3-]. Carbonic acid (H2CO3) is a volatile acid, and its concentration is directly related to the partial pressure of CO2 in equilibrium with the solution in question:
[H2CO3] = α x PCO2
At 37 degrees C, α = 0.03 mmols/mmHg. Combining this relationship with equation 4 yields:
[H+] = Kα x PCO2/[HCO3-] |
|
|
Term
| Why is carbonic acid an excellent buffer? |
|
Definition
| Because its concentration is directly dependent on PCO2, which in turn is regulated by the lungs |
|
|
Term
| To maintain normal HCO3- stores in the body, the kidney has two tasks: |
|
Definition
1. It must recapture all filtered HCO3-
2. It must generate new HCO3- to replace the HCO3- consumed in buffering strong acids in the body. |
|
|
Term
| How does renal bicarbonate reabsorption occur? |
|
Definition
| Bicarbonate is freely filtered across the glomerulus. At a normal plasma concentration (24 mEq/L) and GFR (160 L/day), 3480 mEq is potentially lost to the body each day, and must be recaptured in the renal tubules. The vast majority, ~ 80%, is recaptured in the proximal tubule in the following manner where HCO3- is reabsorbed by H+ secretion, via both NHE3 and the H+ ATPase. The secreted H+ reacts with HCO3- in the tubule urine, forming H2CO3, which is rapidly dehydrated to form CO2 and H2O (facilitated by carbonic anhydrase). The CO2 diffuses rapidly into the cell, combining there with OH- to reform HCO3-, which in turn leaves the basolateral side of the cell (via a specific electrogenic cotransporter). Although seemingly circuitous, this process allows for HCO3- reabsorption and acid excretion to occur by the same mechanism: H+ secretion. |
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|
Term
| After the proximal tubule, how does reabsorption of HCO3- occur? |
|
Definition
| In the thick ascending limb of the loop of Henle, NHE3 (but not H+ ATPase) is present, continuing HCO3- reabsorption. By the early distal tubule, ~90% of filtered HCO3- is recaptured, and the concentration of HCO3- ([HCO3-]) falls to 5-8 mEq/L. The remainder is recaptured by the intercalated cells of the collecting duct, via the H+ ATPase. |
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|
Term
| How is the intercalated cell involved in HCO3 reabsorption? |
|
Definition
| When there is excess HCO3- in the body, the collecting duct can also secrete HCO3- as well via an intercalated cell, in which the H+ ATPase is on the basolateral side and the Cl-/HCO3- exchanger is on the apical side. |
|
|
Term
| What are the two methods of renal acid secretion? |
|
Definition
| 1) titration of filtered buffers, primarily HPO4=, which can accept an H+ and carry it into the urine, and 2) ammonium (NH4+) excretion, which allows for HCO3- generation in the proximal tubule epithelial cell. |
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|
Term
| How does titration of HPO2= occur in the kidney? |
|
Definition
Titration of HPO4= in the collecting duct occurs when the [H+] in the collecting duct is increased (pH is decreased) by H+ secretion via the H+-ATPase in the apical membrane of the intercalated cells. By far the most abundant substance that carries H+ into the urine is ammonium (NH4+).
Ammonium is generated in the proximal tubule by deamination of glutamate to α - keto-glutarate, the latter an organic anion that can be metabolized of CO2 and water, generating 2 new HCO3- ions in the process, which are added to the body. The newly formed NH4+ is secreted via NHE3 (as well as diffusing across the apical membrane). Ammonium is then partially reabsorbed in the loop of Henle, and carried into the renal medulla, where it diffuses into the collecting duct and is “trapped” there by collecting duct H+ secretion, and carried into the urine. |
|
|
Term
| Both HCO3- reabsorption and acid excretion result from what same process? |
|
Definition
| H+ secretion along the nephron, via two apical membrane transport proteins on renal tubule epithelial cells - the Na+/H+ exchanger (NHE3) and the H+ ATPase. |
|
|
Term
| Acid excretion occurs when secreted H+ combines with … |
|
Definition
| filtered phosphate or with ammonia that diffuses into the collecting duct. |
|
|
Term
| What is an excellent source for excreting acid into the urine and how is it produced? |
|
Definition
| Ammonium is a flexible source for excreting acid and generating new HCO3-. It is produced from glutamine in the renal cortex, secreted via NHE3, and excreted via a complex process involving countercurrent concentration, diffusion and H+ secretion in the medullary collecting duct. |
|
|
Term
| What is the typical pH of urine? |
|
Definition
| 5.5 to 6.5, normally free of HCO3- |
|
|
Term
| For a man to be fertile, he must fulfill what three basic requirements |
|
Definition
| (1) Produce semen (sperm and fluids in which sperm is suspended during ejaculation) containing sufficient numbers of healthy sperm. (2) Achieve an erection of sufficient rigidity to deposit semen in the vagina during intercourse, and (3) Ejaculate. |
|
|
Term
| What part of the endocrine system regulates and maintains the male reproductive system? |
|
Definition
| The hypothalmic-pituitary-gonadal axis |
|
|
Term
| What hormones are important in regulating and maintaining the male reproductive system? |
|
Definition
| The hormones involved include GnRH, two gonadotropins (LH, FSH), and androgenic sex steroids (testosterone - T. and it’s metabolite dihydrotestosterone, or DHT). |
|
|
Term
| What are some cellular and endocrinological parallels between the male and female? |
|
Definition
| At the age of 19 or 20, a man is at his reproductive peak, at least in a physiological sense. The system is driven by the pulsatile release of GnRH that stimulates release of the two gonadotropins (LH, FSH), which are also released in a pulsatile fashion. This part of the system is identical in both men and women, although the patterns of secretion differ. In both the male and the female, there is some parallelism in terms of what types of cells are stimulated by the gonadotropins, the cellular signal transduction responses that they elicit, and where they are located relative to the germ cells (egg and sperm), and how they cooperate to produce hormones and physiological effects. |
|
|
Term
| How do LH and FSH differ? |
|
Definition
| Although LH and FSH are both glycoproteins, they are structurally different. Chains of amino acids linked to sugars, the gonadotropins are complex and three-dimensional molecules that are polar and, therefore, unable to easily pass into cells. Instead, they must rely on cellular recognition via receptors expressed on the plasma membrane [3]. Binding to the receptor can elicit a variety of signals within the target cell (the “second messengers”, since the gonadotropin binding to the cell membrane is the “first messenger”) that regulate changes in cellular metabolism, secretion, contractility, hormone production, receptor expression, etc. |
|
|
Term
| Where are Leydig cells and what do they have receptors for? |
|
Definition
| Leydig cells interspersed between the seminiferous tubules (also called interstitial cells for this reason) have receptors for LH. Their having the first letter in common (LH-Leydig) is an easy way to remember this specificity. |
|
|
Term
| What is the action of LH in men? |
|
Definition
| In men, the action of LH [4] is to stimulate the Leydig cells to make the male sex steroid testosterone. |
|
|
Term
| What are the three main classes of sex steroids? |
|
Definition
| progestogens, androgens and estrogens – can be readily identified by the number of carbons. |
|
|
Term
| What is testosterone and how can it be synthesized? |
|
Definition
| Testosterone is an androgen, and there are other androgenic variants and metabolites that exist, but they all have 19 carbons (while progesterone has 21, and estrogens have 18). Testosterone can be made from progesterone (via 17α-hydroxylation followed by cleavage of two carbons), and estrogen can be made from testosterone (via a process of aromatization). |
|
|
Term
| What does FSH bind to and what does it do? |
|
Definition
| FSH binds to the Sertoli cell, which is located within the seminiferous tubule, and stimulates its metabolic activity. The Sertoli cells nurture the developing sperm by secreting nutrients and a fluid that helps wash the sperm out of the tubule and into the rete testis. They also secrete a protein called Androgen Binding Protein, or ABP, which remains in the tubule. Each molecule of ABP can bind many testosterone molecules; by acting as a testosterone ‘sponge’, this protein keeps testosterone concentrations at an elevated level within the tubule. In response to the actions of FSH, Sertoli cells also make a peptide hormone of their own, called inhibin [7], which regulates FSH secretion through negative feedback (just like testosterone regulates LH). |
|
|
Term
| What are Sertoli cells and what do they do? |
|
Definition
| The Sertoli cells nurture the developing sperm by secreting nutrients and a fluid that helps wash the sperm out of the tubule and into the rete testis. They also secrete a protein called Androgen Binding Protein, or ABP, which remains in the tubule. Each molecule of ABP can bind many testosterone molecules; by acting as a testosterone ‘sponge’, this protein keeps testosterone concentrations at an elevated level within the tubule. This testosterone originates from the Leydig cell, and easily diffuses across the outer wall of the tubule into the Sertoli cell. Once it enters the Sertoli cell, it binds to the nucleus to also stimulate Sertoli cell function. Hence Sertoli cells are principally under the control of one gonadotropin (FSH), and one steroid (testosterone), which is produced in, and released from the neighboring Leydig cells. In response to the actions of FSH, Sertoli cells also make a peptide hormone of their own, called inhibin [7], which regulates FSH secretion through negative feedback (just like testosterone regulates LH). |
|
|
Term
| What does GnRH stimulate? |
|
Definition
| The release of LH and FSH |
|
|
Term
| In both Sertoli and Leydig cells the binding of the gonadotropin to a membrane receptor often triggers what? |
|
Definition
| A host of second messengers, cAMP foremost among them. cAMP stimulates other enzymes (like Protein Kinase A, or PKA) that phosphorylate molecules (add a high energy phosphate group) and subsequently alter the metabolic activity of the Leydig and Sertoli cells. |
|
|
Term
| How does testosterone stimulate changes in cell function? |
|
Definition
| Because testosterone is a steroid, it is a non-polar lipid. Unlike FSH and LH, which activate membrane-bound receptors, sex steroids readily diffuse across the cell membrane into the cell’s interior and travel to the nucleus, where they bind to DNA and activate specific genes, leading to changes in cell function (secretory activity, synthesis of other hormones or growth factors). |
|
|
Term
| Some testosterone released from Leydig cells escapes into capillaries. What does this testosterone do? |
|
Definition
| First, it provides a negative feedback signal to the pituitary to control LH secretion. It also regulates and maintains the structure and function of all of the associated secondary sex organs - the tubes (e.g. vas deferens), the glands (e.g. seminal vesicles), the organs (e.g. penis) - of the reproductive tract. Within the testis, the process of spermatogenesis would be abrogated without testosterone, and the individual would likely have a low sperm count and be infertile. The man lacking or deficient in testosterone, might also have different feelings and emotions, since testosterone is important in CNS function. Finally, if the lack of testosterone begins early in life, he would have some visible differences in his genitalia and appearance, lacking many of the secondary sexual characteristics we associate with the adult male. |
|
|
Term
| What actions of testosterone occur in utero? |
|
Definition
| If a child is destined to be a boy, testosterone production is initiated by factors derived from the Y chromosome quite early in pregnancy (weeks 6-8). Its action at this time, along with other factors secreted from the testes, is to shunt the process of sexual differentiation [9] towards the male gender by stimulating the growth of male gonads and accessory ducts and glands. We are all born with primitive gonads and ducts that can develop either into male or female sex organs. The Wolffian duct develops into the male; the Mullerian duct, into the female. Without testosterone, the Wolffian ducts atrophy, and the reproductive organs of the individual become female (default). In a male embryo, however, the female vestiges (Mullerian ducts) involute due to the secretion of antimullerian hormone (secreted from the testes), while the Wolffian ducts are stimulated to grow and differentiate under the influence of testosterone, and develop into the reproductive structures of the male. This process of sexual differentiation is normally completed by week 15 of gestation. |
|
|
Term
| What actions of testosterone and androgens occur during puberty in boys? |
|
Definition
| These promote growth of the secondary sexual organs like the penis and scrotum, stimulate the growth and secretory activity of the epididymis and accessory glands, and facilitate the initiation of spermatogenesis. Androgens also effect changes in the pitch of the voice (via growth of the larynx and thickening of the vocal cords), stimulate muscle development, and development of facial, chest and axillary hair. Testosterone stimulates protein anabolism and bone growth, although it also hastens epiphyseal closure. In the case of testosterone excess, a child may experience accelerated growth, but end up being shorter. Unfortunately, in genetically prone individuals, androgens may also lead to loss of hair on the head (male pattern baldness). |
|
|
Term
| How does testosterone production change after puberty as a man becomes older? |
|
Definition
| After puberty, the adult man produces 6-7 mg of testosterone per day. As the man passes from youth to middle, and then old age [11], this amount slowly declines, reaching a level of 3-4 mg/day in the seventh decade of life, and is reflected in a progressive reduction in circulating concentrations. Because this is a very gradual process, as men age, they do not undergo a sudden cessation of sex steroid production (as women do after menopause), and can remain fertile well into old age. In the adult, testosterone exerts a paracrine influence on spermatogenesis, maintains the size and function of secondary sexual organs (e.g. vas deferens, epididymis, seminal vesicles, and prostate); preserves muscle mass, and affects behavior via its actions on the CNS. It also has metabolic effects (increases the basal metabolic rate), and stimulates the production of red blood cells (erythropoiesis), which is why men tend to have hematocrit values that are several points higher than those of women. |
|
|
Term
|
Definition
| Once it is absorbed into the bloodstream, testosterone circulates bound to plasma proteins, so that the effective (or “free”) concentration is only 2-3% of the total hormone. Within many tissues, testosterone functions as a pro-hormone, and is converted into dihydrotestosterone (DHT) [12], an active metabolite. The importance of DHT becomes evident when one considers the fate of individuals who lack the enzyme that converts T into DHT (5α-reductase, [13]). DHT is critical for directing the normal development of the male external genitalia during embryonic life and, without it, the female structures may predominate, even though the sex is male, and underdeveloped and undescended testes may be present in the inguinal region. Hence, the individual is a genetic male (has a Y chromosome), but has the phenotypic appearance of a female. |
|
|
Term
| What enzyme is important in creating DHT? |
|
Definition
| 5α-reductase converts testosterone into DHT |
|
|
Term
|
Definition
| The importance of DHT becomes evident when one considers the fate of individuals who lack the enzyme that converts T into DHT (5α-reductase, [13]). DHT is critical for directing the normal development of the male external genitalia during embryonic life and, without it, the female structures may predominate, even though the sex is male, and underdeveloped and undescended testes may be present in the inguinal region. Hence, the individual is a genetic male (has a Y chromosome), but has the phenotypic appearance of a female. |
|
|
Term
|
Definition
| In other tissues (such as fat, liver, skin and brain), the enzyme aromatase [14] converts testosterone into estrogen within the cell (note - unlike T, DHT can not be aromatized). |
|
|
Term
| What problems can occur with the metabolysis of testosterone to estrogen? |
|
Definition
| A number of conditions can include visible feminization, including breast development (gynecomastia). Some causes of feminization may be treatment of hypogonadal males with high doses of testosterone or the use of anabolic steroids by athletes. In both cases, the excess in testosterone may result in a spillover in which more estrogen is produced as well. Estrogen-secreting tumors will, of course, produce many of the same symptoms of feminization. |
|
|
Term
| Is there a correlation between testosterone and sexual desire? |
|
Definition
| In normal men, there is no clear correlation between circulating testosterone concentrations and sexual desire [15]. If an adult man is castrated, he will experience a gradual decline, but not a complete elimination of sexual interest and activity. There is also no obvious correlation with impotence or homosexuality. |
|
|
Term
| What is the "sufficient quantity" of sperm necessary for fertility in the male? |
|
Definition
| In general, concentrations in excess of 20 million sperm per ml of semen are considered normal; values below 20 million/m are marginal, and below 15 million/ml may explain infertility. Many men have sperm counts on the order of 50-200 million/ml; therefore, it is not unusual for the total ejaculate, which has a volume of 3-5 ml, to contain half- or even one billion sperm. The process of spermatogenesis is active and ongoing throughout adult life in the male. |
|
|
Term
| Where do sperm go after production within seminiferous tubules? |
|
Definition
| Sperm are transported through a series of ducts (rete testis; efferent ductules; epididymis; vas deferens). They may be stored in the epididymis or vas deferens for a considerable period of time (weeks); urethra prior to ejaculation. |
|
|
Term
| What is the structure of the seminiferous tubules? |
|
Definition
| Each testis contains hundreds of tightly packed seminiferous tubules ranging from 150-250 um in diameter, and 30-70 cm (1-2 feet) in length. The tubules are packed into lobules and both ends of any one tubule open into the rete testis. Hence, each tubule is really a loop. The interior of the seminiferous tubule is avascular, and lined with Sertoli cells [18], which are large, irregularly shaped cells that extend from the basement membrane of the tubule into the lumen. |
|
|
Term
| What is the type of junction between the Sertoli cells in the seminiferous tubules and why are they important? |
|
Definition
| Sertoli cells are connected to each other by tight junctions that effectively divide each tubule into a basal (outer) and an adluminal (inner) compartment. Tight junctions between adjacent Sertoli cells limit the transport of macromolecules and fluid from the interstitial space (space between the tubules, which contains capillaries and Leydig cells) and therefore create a barrier between the outside of the tubule and its lumen (the blood-testis barrier). By virtue of the blood testis barrier, the adluminal compartment is an immunologically privileged site since spermatozoa that develop within it are not recognized as “self”, and can potentially trigger an immune reaction. This can occur following testicular injury or vasectomy, or in some autoimmune diseases, and leads to the production of anti-sperm antibodies that destroy the sperm and may render the male infertile. |
|
|
Term
|
Definition
| The progenitor cells for the production of sperm are the spermatogonia [19]. These are non-differentiated cells that are found in the basal compartment of the seminiferous tubules, and that constantly undergo mitotic division, thereby replenishing themselves. The process of spermatogenesis is initiated when some of the spermatogonia grow into primary spermatocytes. |
|
|
Term
| What are primary spermatocytes? |
|
Definition
| The process of spermatogenesis is initiated when some of the spermatogonia grow into primary spermatocytes [20], and migrate across the junctional complexes into the adluminal compartment. Subsequently, they undergo two meiotic divisions, leading to the creation of four haploid cells. |
|
|
Term
| What is the secondary spermatocyte? |
|
Definition
| The first haploid cell (n), before the second (equatorial) meiotic division |
|
|
Term
| What are the ways that genetic diversity occurs in sperm? |
|
Definition
| During meiosis, the maternal and paternal chromosomes align in a random way, leading to 223 possible combinations when they separate. This is similar to the number of combinations possible if one lays 23 coins out on a table, and begins to flip them over in various combinations (head-tail-tail... vs. head-tail-head... and so on). This alone results in approximately 8 million possible combinations! In addition, there is a certain degree of recombination that occurs (genetic information carried on one chromosome may become relocated to another position on a different chromosome), resulting in an even greater genetic diversity [22]. For this reason, it is possible to have millions of sperm, with no two having exactly the same genetic profile. |
|
|
Term
| What occurs in the equatorial division? |
|
Definition
| The second meiotic division, this occurs when two secondary spermatocyte form four spermatids. |
|
|
Term
| What changes occur as a spermatid matures into a sperm? |
|
Definition
| Morphologically, spermatids are unremarkable, and look like any other cell, except that they are haploid. The small, round and undistinctive appearance of the spermatid then begins to undergo a morphologic change into what we would recognize as a sperm. There is a condensation of the nucleus (increase in its density), and loss of cytoplasm. The acrosome, a lysosome-like structure unique to spermatozoa buds from the Golgi apparatus, flattens, and comes to rest on top of the head of the sperm like a cap. The centrioles migrate to the caudal pole and form the tail by producing a long axial filament composed of 9 peripheral doublet microtubules arranged around a central pair that is referred to as the axoneme [24]. The axoneme is wrapped in a fibrous sheath, giving some rigidity to the tail, which is basically similar in structure to any cilium or flagellum. |
|
|
Term
| What is the name of the process where spermatids become sperm? |
|
Definition
|
|
Term
| What are the characteristics of a fully matured sperm cell? |
|
Definition
| The acrosome capping each spermatozoon contains a variety of proteolytic enzymes such as hyaluronidase, acrosin, neuraminidase, phospholipase A, and esterases. The head of the sperm contains the DNA, and, at its caudal end, narrows to form the neck, which is a transition zone to the midpiece. The midpiece has the axoneme in its center, and a well organized spiral sheath of mitochondria wound around the central filament. These produce ATP to fuel locomotion via the beating of the tail, and produce energy from nutrients present in the fluid within which they are suspended. The tail propels the sperm by a twisting motion derived from interactions between tubulin fibers and dynein side arms, a process that utilizes a magnesium-dependent ATPase. The head of the sperm is only a few microns in diameter, and can exceed 50 um in length. |
|
|
Term
| What is in the head of the sperm cell? |
|
Definition
| The acrosome capping each spermatozoon contains a variety of proteolytic enzymes such as hyaluronidase, acrosin, neuraminidase, phospholipase A, and esterases. The head of the sperm contains the DNA, and, at its caudal end, narrows to form the neck, which is a transition zone to the midpiece. |
|
|
Term
| What is in the midpiece of the sperm cell? |
|
Definition
| The midpiece has the axoneme in its center, and a well organized spiral sheath of mitochondria wound around the central filament. These produce ATP to fuel locomotion via the beating of the tail, and produce energy from nutrients present in the fluid within which they are suspended. |
|
|
Term
| What is in the tail of the sperm cell? |
|
Definition
| The tail propels the sperm by a twisting motion derived from interactions between tubulin fibers and dynein side arms, a process that utilizes a magnesium-dependent ATPase. The head of the sperm is only a few microns in diameter, and can exceed 50 um in length. |
|
|
Term
| How long does sperm generation take? |
|
Definition
| In a fertile male, the process of spermatogenesis generates 100-200 million sperm per day through a process that is synchronized, and carried out in close physical association the Sertoli cells, which ‘nurture’ the developing sperm (Sertoli cells are also called sustenacular cells). The entire process takes approximately 10 weeks to complete, and is under the direct regulation of the Sertoli cell by FSH. |
|
|
Term
| How do sperm taken efferent ductules differ from those exiting the tail of the epididymis? |
|
Definition
| Sperm taken from the efferent ductules (prior to entering the epididymis) are completely immotile, while those exiting from the tail of the epididymis have acquired motility. |
|
|
Term
| What is decapitation and capitation in sperm? |
|
Definition
| Sperm become decapacitated during their passage through the epididymis due to the absorption of various lipids (such as cholesterol) onto the head. The process of capacitation involves removal, or washing off of these lipids, and normally occurs only after ejaculation, once the sperm are within the female reproductive tract. |
|
|
Term
| What is the general composition of male ejaculate? |
|
Definition
| Although the number of sperm produced daily is staggering, sperm only comprise a small fraction (about 5-10%) of the total ejaculate. The remaining 90-95% is composed of fluids derived from the seminal vesicles (approximately 60%), the prostate (30%), and accessory glands called the bulbourethral (or Bartholin’s) glands (<5%). There are also urethral glands sprinkled along the urethra that secrete a lubricating mucus, making the walls or the penile urethra slippery and providing less resistance during the process of ejaculation. |
|
|
Term
| What are prostatic secretions? |
|
Definition
| Milky, thin and alkaline, they contain prostate-specific antigen (PSA) which is often elevated in prostate cancer, and can therefore be used as a marker for prostatic malignancy. Prostatic secretions also contain other enzymes, most notably spermine phosphate or phosphatase, which are used as markers for semen in crime scene investigation, and in medico-legal issues. |
|
|
Term
| What are the secretions of the seminal vesicles? |
|
Definition
| The secretions of the seminal vesicles [27] are sticky and rich in mucus, and contain fructose (the principal energy substrate for glycolysis in ejaculated sperm) ascorbic acid, and prostaglandins. Prostaglandins can induce smooth muscle contractility, and aid fertilization by producing reverse peristalsis within the female reproductive tract. They were first isolated from semen and assumed to originate in the prostate (a fact that was subsequently found not to be true), but the name has remained in use nonetheless. |
|
|
Term
| What is the clotting-declotting system in semen? |
|
Definition
| This system is derived from clotting enzymes in prostatic fluid, and fibrinogen in seminal vesicle fluid. Their coordinated action results in the formation of a loose coagulum, followed by liquefaction shortly after ejaculation |
|
|
Term
| At what temperature do the human testes function? |
|
Definition
| The human testes do not function normally at body temperature, and must be maintained at 2–3 oC below core body temperature. This is accomplished by several concurrent mechanisms of thermoregulation [28], all of which depend on the testes being suspended away from the body. |
|
|
Term
|
Definition
| During pregnancy, the testes form within the body cavity, but descend into the scrotum between 7 months and term. Failure to do so is termed cryptorchidism [29] (or cryptorchism) and occurs in 2-3% of male infants. Often, this condition resolves on its own in the month or two after birth, although it sometimes does require surgical intervention. |
|
|
Term
| What muscle governs the distance of the testes from the body? |
|
Definition
|
|
Term
| What mechanisms control the temperature of the testes? |
|
Definition
| the distance of the testes from the body can be regulated by the contraction or relaxation of a thin, sheet-like skeletal muscle called the cremaster (mechanism 1, [30]). Also, the scrotum is well-endowed with sweat glands (mechanism 2, [31]) that facilitate evaporative cooling, thereby lowering the testicular temperature. Failure to correct cryptorchidism is associated with a much higher incidence of testicular cancer. A third important mechanism is that of countercurrent heat exchange (mechanism 3, [32]) between the testicular arteries and the veins. |
|
|
Term
| How does the countercurrent heat exchange function in temperature control of the testes? |
|
Definition
| Blood flows to each testis via the testicular artery, which ramifies within the testis into smaller arteries and capillaries that course between the seminiferous tubules. The blood returns from the testis via a specialized tangle of veins called the pampiniform plexus [33]. Because it is wrapped around the spermatic artery, this anatomic arrangement facilitates a countercurrent exchange of heat, i.e. warm blood flowing to the testis is cooled by venous blood within the pampiniform plexus. Put differently, the cool venous blood is re-warmed by the heat given up by the warm arterial blood within the testicular artery (mechanism 3). |
|
|
Term
| What happens when the pampiniform plexus becomes varicosed? |
|
Definition
| This compromises the normal flow of blood, and the process of heat exchange. This condition is called a varicocoele [34], and usually (>90% of the time) occurs on the left side. This is related to differences in venous anatomy, which is not symmetrical. Varicocoele may be present in 5-15% of men, and is thought to account for about 15% of male infertility. |
|
|
Term
| How do the right and left testes differ in venous anatomy? |
|
Definition
| While the right testis drains into the inferior vena cava, venous blood from the left testicle passes into the renal vein. Venous pressure may be higher in the renal vein and, combined with the longer length of the left spermatic vein, and the fact that it joins the renal vein at a right angle, the entry of testicular venous blood is impeded, and backpressure may lead to venous overdistension, a primary cause of varicose veins. |
|
|
Term
| Other than thermal damage, how can spermatogenesis be compromised? |
|
Definition
| By exposure to radiation (because of the continuously dividing spermatogonia). Also, epididymal defects that result in immotile sperm, and structural defects (two heads, bent tails; absence of an acrosome; defective genetic material) may all contribute to reducing the viability of sperm and, hence, male fertility. |
|
|
Term
| What is semen analysis? How is it performed? |
|
Definition
| This is useful for evaluating sperm number, viability, motility and frequency of morphologic defects. The man is asked to refrain from sexual activity for at least 48h, as repeated ejaculations result in a reduction in sperm number and ejaculate volume, potentially yielding a false positive diagnosis (you think you identified the problem, but really did not). |
|
|
Term
| How can the viability of the acrosome be assessed? |
|
Definition
| Although the acrosome is not readily apparent through a light microscope, specialized stains can be applied to selectively stain for the presence of acrosomal enzymes and an intact acrosomal membrane. |
|
|
Term
| What is spermatogenesis ultimately dependent upon? |
|
Definition
| Spermatogenesis is ultimately dependent upon the hypothalamus, pituitary, and normal Leydig and Sertoli cell function. A defect in any part of this endocrine/cellular system may be responsible for low sperm count and male factor infertility. |
|
|
Term
| What % of infertility is due to males, and what % to females? |
|
Definition
| Within the general population, male factor infertility is responsible for approximately 40% of total infertility; female infertility accounts for the remaining 60%. |
|
|
Term
| How does erection occur in males? |
|
Definition
| Erection is associated with sexual arousal emanating from sexually related psychic and/or physical stimuli. Nerve impulses originating from the genitalia, skin or brain (limbic area) elicit a neurovascular reflex [36] that is carried to the penis by parasympathetic nerves [37] emerging in the sacral region of the spinal cord via the cavernous nerve branches of the prostatic plexus. The penis is composed of three cords of erectile tissue - The basocentral corpus spongiosum (which also forms the glans, or head of the penis and contains the urethra) and two corpora cavernosa, situated in a horizontal plane above the corpus cavernosum. Note: Sometimes, the corpus spongiosum is also referred to as the urethral corpus cavernosum. |
|
|
Term
| What role does NO play in male erection? |
|
Definition
| Nerve stimulation elicits release of vasodilatory neurotransmitters, particularly nitric oxide (NO) [38], from nerves located on small muscular penile helicene arteries [39]. These vessels are normally under predominant sympathetic influence and operate in a constricted state, restricting the amount of blood flowing to the flaccid penis. During erection, nitric oxide binds to and stimulates the enzyme guanylate cyclase within arterial smooth muscle. This results in an increase in cytosolic cGMP, and subsequent relaxation and vasodilation [40]. Blood flow increases, and fills the erectile tissue with blood (the filling phase), causing the penis to elongate and become tumescent. As the erectile tissues expand, they compress the veins, which are located peripherally, allowing maximal (nearly systemic) pressure to develop in the cavernosum and spongiosa (the tumescent [41] phase). |
|
|
Term
| What is the tumescent phase? |
|
Definition
| When erectile tissues expand and compress veins, thus allowing for maximal pressure in the cavernosum and spongiosa. |
|
|
Term
| What nerves release NO in the penis? |
|
Definition
| Nerves located on the small muscular penile helicene arteries |
|
|
Term
| How does erection cease in the male? |
|
Definition
| Once nerve stimulation ceases, an enzyme called Phosphodiesterase 5 [42] - also present within vascular smooth muscle - catalyzes the breakdown of cGMP to inactive (non-vasodilatory) metabolites, and the helicene arteries reconstrict. |
|
|
Term
| How does Viagra function? |
|
Definition
| Sildenafil (Viagra) [43] stimulates erection by inhibiting Phosphodiesterase 5, thereby maintaining elevated cGMP levels, and vasodilation. |
|
|
Term
| What occurs during the emission phase of male ejaculation? |
|
Definition
| The efferent arc f the ejaculation reflex originates in the lumbar spinal cord (L1, L2), and begins with the emission phase [45], in which sperm and associated fluids from the epididymis and vas deferens are propelled into the urethra by peristaltic contractions of the vas in response to nerve stimulation. At the same time, the capsules of the seminal vesicles and prostate constrict, increasing intraglandular pressure and forcing the secretions into the urethra, where they mix with sperm (suspended in concentrated form in fluids derived from the seminiferous tubules, epididymis and vas). |
|
|
Term
| What occurs during the ejaculatory phase of male ejaculation? |
|
Definition
| The ejaculatory phase [46] is initiated after emission - the filling of the urethra initiates sensory signals via pudental nerves that travel to the sacrospinal region of the cord. A spinal reflex mechanism induces rhythmic contractions of the striated bulbospongiosus muscles surrounding the urethra, and propelling the semen out of the tip of the penis. |
|
|
Term
| What are the four main categories of male infertility? |
|
Definition
| disorders of spermatogenesis, obstruction of efferent ducts, disorders of sperm motility, and sexual dysfunction |
|
|
Term
| What is the difference between impotence and infertility? |
|
Definition
| The former term is narrower than the latter, and is defined as “the consistent inability to achieve or sustain an erection of sufficient rigidity for sexual intercourse”. It may be due to many different causes, including spinal cord injury, autonomic and peripheral neuropathy, endocrine disorders, psychogenic disorders (e.g. performance anxiety and depression), atherosclerosis (yes, it can occur there too), and drug-induced effects. Anything that affects the neurovascular pathway we already discussed may affect sexual function, even physical compression (as in poorly designed bicycle seats) or loss of interest secondary to antidepressant therapy. In this regard, the use of Prozac and similar compounds has been associated with a loss of libido and impotence. |
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Term
|
Definition
- oblique passage about 4 cm long through abdominal wall that allows some structures to pass to and from the scrotum in males
- in females it permits passage of the round ligament from the uterus to the labia majora
- courses from deep inguinal ring inferomedially to the superficial inguinal ring and lies parallel to the inguinal ligament |
|
|
Term
| Superficial inguinal ring contents |
|
Definition
- opening in the aponeurosis of the external oblique just superolateral to the pubic tubercle through which the spermatic cord or round ligament of the uterus passes
- the ilioinguinal nerve (L1, referred to as ant. scrotal/labia after exits) and the genital branch of the genitofemoral nerve (L1, 2) pass through the superficial ring |
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|
Term
| Superficial inguinal ring size and shape |
|
Definition
- larger in men than women
- narrow triangle pointing superolaterally in same direction as the fibers of the external oblique aponeurosis
- base is crest of pubis
- sides are margins of the opening in the aponeurosis (lateral and medial crura)
1. Lateral crus: stronger and formed by portion of inguinal ligament attached to pubic tubercle forms a narrow trough upon which the spermatic cord or round ligament rests
2. medial (or superior) crus is thin and flat aand is part of the external oblique aponeurosis medial to the opening |
|
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Term
|
Definition
- connect lateral and medial crura and prevent overdistention of the superficial inguinal ring
- these interlacing fivers are formed from the aponeurosis of the external oblique |
|
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Term
|
Definition
- outpouching of transversalis fascia where the spermatic cord or round ligament leaves the ant. abdominal wall
- lies 1 cm sup. to the midpoint of the inguinal ligament
- inferior epigastric vessels are medial to it
- it formed prenatally when the processes vaginalis evaginated through transversalis fascia |
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|
Term
| Inguinal (Poupart's) ligament |
|
Definition
- thickened lower border of the aponeurosis of the external oblique
- extends from ant. superior iliac spine to the pubic tubercle ina curved line which folds post
- its medial attachment on to the pubic tubercle forms a narrow sling for support of the spermatic cord or round ligament of the uterus |
|
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Term
|
Definition
- portion of the inguinal ligament that fails to reach the pubic tubercle and is attached to the pubic ramus
- lies almost horizontally in the erect posture with the spermatic cord or round ligament of the uterus resting on its sup surface
- the medial wall of the femoral ring lies against its concave lateral border |
|
|
Term
| Indominate (Gaullaudet's) fascia |
|
Definition
- deep fascia on the external surface of the external oblique m. and aponeurosis
- continued down into the scrotum enclosing the spermatic cord and testis in a sheath called the external spermatic fascia |
|
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Term
|
Definition
- thin, muscular layer that spreads out over the spermatic cord and testis in a series of loops
- it arises in the middle of the inguinal canal as a continuation of the internal oblique m.
- the cremaster muscle draws the testis up toward the inguinal ring
- it is innervated by the genital branch of the genitofemoral nerve |
|
|
Term
|
Definition
- the internal investing layer of deep fascia which lines the entire abdominopelvic wall
- a tubular prolongation of this fascia invest the spermatic cord as it leaves the abdominal cavity and is then known as internal spermatic fascia |
|
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Term
|
Definition
- Collection of structures that traverse the inguinal canal
- includes vas deferens and its artery, the testicular and cremasteric arteries, the pampiniform plexus aof veins, lymphatics, nerves and the remains of the processes vaginalis |
|
|
Term
| inguinal (Hesselbach's) triangle |
|
Definition
- an area of the ant. abdominal wall bounded by the inf epigastric vessels, inguinal ligament, and the lateral border of the rectus abdominis
- direct inguinal hernias leave the abdomen through this triangle |
|
|
Term
| Round ligament of the uterus |
|
Definition
| - one of the two fibrous remnants of the gubernaculum in the female, the other being the ligament of the ovary |
|
|
Term
|
Definition
- protrusion of an organ or a tissue through the wall of a cavity that normally contains it
- can occur in almost any place in the body
- named by their time of onset (congenital or acquired) and location (umbilical, diaphragmatic, femoral, inguinal etc) |
|
|
Term
|
Definition
- during development there is a natural herniation of the bowel into the umbilical cord, the bowel returns to the abdominal cavity before the birth
- linea alba fails to fuse properly resulting in a weak area which is subject to herniation (congenital umbilical hernia)
- an umbilical hernia in adults occurs when the umbilicus becomes greatly stretched allowing omentum or intestines to pass through it (acquired umbilical hernia) |
|
|
Term
| Diaphragmatic (hiatal) hernia |
|
Definition
- abnormal openings in the diaphragm which permit herniation of abdominal viscera into the thoracic cavity
- congenital are present at birth and are due to failure of the diaphragm to develop properly
- acquired diaphragmatic are located at the esophageal hiatus and usually resut in a portion of the stomach protruding into the thoracic cavity |
|
|
Term
|
Definition
- protrusions of abdominal viscera or omenta into femoral canal lateral to the lacunar ligament
- these hernias are subject to strangulation (compression resulting in loss of blood supply which could lead to gangrene due to sharp edge of the ligament |
|
|
Term
| Inguinal hernias characterizations |
|
Definition
- congenital or acquired
- direct or indirect
- complete or incomplete |
|
|
Term
| congenital inguinal hernia |
|
Definition
- considered indirect, thus pass through the deep ring, follow the entire length of the canal and exit the superficial ring
- result from failure of the processus vaginalis (a sleeve of parietal peritoneum) to close during development
- because the processus remains open intestines can pass into the scrotum/labia majora |
|
|
Term
|
Definition
- occurs after birth particularly in adults with poor abdominal muscle tone
- Indirect: pass through deep ring lateral to inferior epigastric vessels
- Direct: pass throigh the abdominal wall medial to the ingerior epigastric vessels through an area called the inguinal (Hesselbach's) triangle
- direct hernias due not pass through the deep ring but enter the canal through its posterior wall and can then continue through the superficial inguinal ring to reach the scrotum/labia majora |
|
|
Term
|
Definition
| - one which has passed through the superficial ring |
|
|
Term
|
Definition
| - one which has passed through either the deep ring or the post. wall of the inguinal canal but has not gone through the superficial ring |
|
|
Term
| Rectus abdominis muscle and sheaths |
|
Definition
- enclosed in a sheath which holds it in position but does not restrict its motion during contraction
- sheath is formed by aponeuroses of the external oblique, internal oblique and transversus muscles
- at the lateral border of the rectus muscle this sheath divides into an ant. layer which passes ventral to the muscle and a post layer which passes dorsal to the muscle
- midway between the umbilicus and pubis, the post. layer of the internal oblique rectus muscle
- the line formed dorsal to the rectus abdominis in this region is called the arcuate line |
|
|
Term
|
Definition
- may be divided into 3 parts:
1. above the costal margin
2. from the costal margin to the arcuate line
3. from the arcuate line to the pubis
- lateral border of the rectus sheath is called the semilunar line |
|
|
Term
| Contents of rectus sheath |
|
Definition
1. rectus abdominis and pyramidalis muscles
2. superior and ingerior epigastric vessels
3. the termination of the lower 5 intercostal nerves (7-11), the 12th (subcostal) thoracic nerve, and their accompanying vessels |
|
|
Term
| Innervation of abdominal wall (general) |
|
Definition
- like thorax the ant. abdominal wall is innervated by ventral rami
- they are motor to ab muscles and sensory to both skin and parietal peritoneum
- carry sympathetic fibers and usually run inthe plane between internal oblique and transversus abdominis muscles
- T7 - L1 |
|
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Term
|
Definition
| - skin surrounding belly button |
|
|
Term
|
Definition
| innervation above umbilicus |
|
|
Term
|
Definition
innervation below umbilicus
- found in both ilioinguinal and iliohypogastric nerves
- doesn't enter rectus sheath but is cutaneous to the skin near the pubic symphysis and groin |
|
|
Term
| Arteries to the anterior abdominal wall |
|
Definition
1. External iliac
- inferior epigastric
- deep circumflex iliac
2. Femoral artery
- superficial circumflex iliac
- superficial epigastric
3. Aorta
- lumbar
- intercostal
4. Internal thoracic
- superior epigastric |
|
|
Term
| Superficial fascia of ant. abdominal wall |
|
Definition
- continuous with superficial fascia of thorax, thigh and back
- inferior to umbilicus the fascia can be divided into two layers a fatty layer and a membranous layer (deeper) |
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|
Term
| Fatty layer of superficial fascia (Camper's fascia) |
|
Definition
- may be several inches thick in obese individuals
- in female it retains some adipose tissue as it continues into the labia majora
- in male it continues down on the penis and scrotum, this layer loses its fat, fuses with the membranous layer and forms dartos fascia or tunic |
|
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Term
| Membranous layer of superficial fascia (Scarpa's fascia) |
|
Definition
- contains no adipose tisssue.
- it forms the fundiform ligament of the penis/clitoris |
|
|
Term
| Deep fascia of abdominal wall |
|
Definition
- fascia that is closely applied to the muscles
- deep fascia on the outside of the abdominal muscles which is called innominate fascia, and deep fascia on the internal side of the muscles called transversalis fascia |
|
|
Term
|
Definition
- external investing layer
- covers the superficial surface of the muscles and aponeurosis on the abdomen
- in inguinal region forms the external spermatic fascia which covers the spermatic cord and the testis
- over the inferior end of the linea alba the deep fascia is thickened into a strong fibrous triangle
- the suspensory ligament of the penis/clitoris which attaches the dorsum of the clotoris/penis to the symphysis pubis |
|
|
Term
|
Definition
- internal investing layer
- lines the entire internal muscualr surface of the abdominopelvic wall
- continuous with the endothoracic fascia of the thorax
- various subdivisions take on special names: psoas, iliacus, and obturator fascia are names given to transversalis fascia on muscles with corresponding names
- this fascia also covers aponeuroses, bones and ligaments ont he internal surface of the abdomen
- the fascia covering the intraabdominal surface of the iliacus and psoas follows these muscles deep to the inguinal ligament out into the thigh and becomes the post. layer of the femoral sheath |
|
|
Term
|
Definition
- extraperitoneal areolar tissue
- lies between transversalis fascia and peritoneum
- abdominopelvic organs, autonomic nerves, and blood vessels are in this fascial layer
- it also persists in mesenteries
- in other areas, such as on the liver, spleen and in the lesser omentum, it disappears
- all visible fat in the abdominopelvic cavity is in the subserous fascia |
|
|
Term
|
Definition
- similar to pleura and pericardium in that it is a serous membrane consisting of parietal and visceral layers
- these layers are separated from each other by a thin film of serous fluid to facilitate the movements of abdominal viscera
- the most mobile parts of the intraabdominal GI tract are surrounded by visceral peritoneum
- The peritoneum passes from GI tract to the post. abdominal wall as two parallel layers (mesentery or ligament)
- these layers are separated by a small amount of subserous fascia in which blood vessels, lymphatics and nerves run to and from the viscera
- where the layers meet the post. abdominal wall they become continuous with parietal peritoneum, which forms a single layer on the internal surface of the abdominal wall |
|
|
Term
|
Definition
L: stomach, small intestine, large intestine
SP: somatostatin
A: decreased secretion by nearby enteroendocrine cells |
|
|
Term
|
Definition
| L: stomach, small intestine, |
|
|
Term
|
Definition
L: Stomach
SP: Histamine
A: increase HCL secretion |
|
|
Term
|
Definition
L: stomach, small intestine
SP: gastrin
A: increased HCL secretion, gastric motility, gastric emptying, proliferation of gastric epithelial cells |
|
|
Term
|
Definition
L: small intestine
SP: cholecystokinin
A: stim, gallbladder contraction, sphincter of oddi relaxation, pancreatic secretion, decreased gastric motility |
|
|
Term
|
Definition
L: small intestine
SP: gastric inhibitory peptide
A: decreased HCL secretion, increased insulin secretion |
|
|
Term
|
Definition
L: small intestine
SP: secretin
A: stimulates release of bicarbonate-rich fluid from pancreas |
|
|
Term
|
Definition
- 3 groups:
1. gastrin family
2. secretin family
3. those do not fit in either family |
|
|
Term
| Gastrin family of GI hormones |
|
Definition
| - Includes gastrin and CCK, as well as variants of each of these peptides, members of the gastrin family share an identical 5 amino acid C-terminus, which is responsible for receptor binding |
|
|
Term
| Secretin Family of GI hormones |
|
Definition
- includes secretin, GIP, vasoactive intestinal peptide
- members of the secretin family share sequence homology throughout the structure, but no active fragment
- in other words the entire sequence is necessary for activity |
|
|
Term
|
Definition
- released from enteroendocrine (D) cells in response to meal and acid as well as by neural and hormonal factors.
- inhibits secretion, motility and hormone release thoughout gut
- found in nerves of the gut and brain and in endocrine cells of pituitary as well as paracrine cells of gastric mucosa and pancreas |
|
|
Term
|
Definition
- released from intestinal endocrine cells in response to a decrease in blood glucose
- causes liver to increase glycogenolysis and gluconeogenesis as well as increase lipolysis |
|
|
Term
| Pancreatic polypeptide family |
|
Definition
- pancreatic polypeptide (PP) released from pancreas in response to a meal (especially amino acids) and peptide YY (PYY) released from ileum in response to lipids
- physiological effect is inhibition of pancreatic enzyme secretion and an indirect indirect relaxation of gallbladder.
- PYY may play a role in feeding behavior/satiety
- a third member of this family, neuropeptide Y (NPY), is found in enteric nerves
- these related peptides can all mimic each other's actions at high concentrations |
|
|
Term
|
Definition
| - G cells in the gastric antrum |
|
|
Term
| Gastrin targets and secretion method |
|
Definition
- ECL cells and parietal cells
- stimulates gastric acid via exocrine secretion |
|
|
Term
| Stimulus for gastrin release |
|
Definition
- peptides and amino acids in lumen
- gastrin releasing peptide and ACh released by nerves |
|
|
Term
| Gastrin release inhibition |
|
Definition
- if pH is less than 1.5
- somatostatin |
|
|
Term
| Cholecystokinin (CCK)is secreted by.. |
|
Definition
| - enteroendocrine (I) cells of the small intestine |
|
|
Term
| Cholecystokinin (CCK) targets |
|
Definition
1. gallbladder
2. pancreas
3. gastric smooth muscle
4. nerves |
|
|
Term
| Exocrine secretion of cholecystokinin |
|
Definition
- stimulates pancreatic secretion
- potentiates bicarbonate secretion |
|
|
Term
| Motility stimulation by cholecystokinin |
|
Definition
stimulates:
- gallbladder contraction
- sphincter of oddi relaxation
- inhibits gastric emptying |
|
|
Term
| Cholecystokinin hunger signal |
|
Definition
| - stimulates satiey (a feeling of having had enough to eat) |
|
|
Term
| Stimulus for release of secretin |
|
Definition
| - acids in small intestine |
|
|
Term
| Gastric inhibitory peptide (GIP) is secreted by |
|
Definition
| - enteroendocrine (K) cells in the small intestine |
|
|
Term
| Targets of gastric inhibitory peptide (GIP) |
|
Definition
| - beta cells of the endocrine pancreas |
|
|
Term
| Endocrine secretion by gastric inhibitory peptide |
|
Definition
| - stimulates insulin release (feed-forward mechanism) |
|
|
Term
| Exocrine secretion of gastric inhibitory peptide (GIP) |
|
Definition
| - inhibits acid secretion |
|
|
Term
| stimulus for gastrin inhibitory peptide (GIP) release |
|
Definition
| - glucose, fatty acids and amino acids in the small intestine |
|
|
Term
| Motilin is secreted by... |
|
Definition
| - enteroendocrine (Mo) cells in the small intestine |
|
|
Term
|
Definition
| - smooth muscle of antrum and duodenum |
|
|
Term
|
Definition
| - stimulates migrating motor complex |
|
|
Term
| Stimulus for release of motilin |
|
Definition
- fasting
- periodic release every 1.5-2 hrs by neural stimulus |
|
|
Term
| Motilin and digestive association |
|
Definition
- changes associated with both constipation and diarrhea
- relationship unclear |
|
|
Term
| Retroperitoneal structures |
|
Definition
| - located posterior to parietal peritoneum and are called primary or secondary - depending upon where they originating |
|
|
Term
| Main patterns of motility |
|
Definition
- mixing (segmentation)
- propulsion (peristalsis) |
|
|
Term
| Electrical conduction of smooth muscle in GI tract |
|
Definition
| - gap junctions in between smooth muscle cells allow for electrically coupled |
|
|
Term
| Interstitial cells of cajal |
|
Definition
- ICCs
- specialized group of cells in the intestinal wall that form networks and transmit information from enteric neurons to smooth muscle cells
- "pacemaker" cells of the gut, have the capacity to generate the basic electrical rhythm or slow waves which is a consistent feature of GI smooth muscle |
|
|
Term
|
Definition
- GI smooth muscle from the distal stomach to the rectum undergoes cycles of contraction and relaxation
- associated with spontaneous cycles of membrane depolarization and repolarization |
|
|
Term
| Slow wave frequence in stomach and intestine |
|
Definition
Stomach: 3-5/min
Intestine: 12-20/min
- frequency set by local ICC then transmitted to muscle by gap junctions |
|
|
Term
| Slow waves and action potentials |
|
Definition
- can give rise to action potential depending on excitability
- amplitude of slow waves can be modulated by neural and hormonal factors and it will determine whether action potentials occur or not |
|
|
Term
| Slow waves and contraction |
|
Definition
- contraction length of smooth muscle depends on duration of slow wave
- contractile force is graded according to amount of Ca2+ that enters fiber
- magnitude related to the number of action potentials fired during the slow wave |
|
|
Term
| Chemical messengers and smooth muscle action potentials |
|
Definition
- those released close to smooth muscle cells alters the resting membrane potentialsof the cells which makes the oscillations in membrane potential (slow waves) more or less likely to reach threshold and initiate an action potential
- these inputs modulate the amplitude and duration of the slow wave and related contractions |
|
|
Term
|
Definition
- sustained for minutes to hours, best represented by sphincters that act as one way vales to prevent retrograde movement of material from distal to more proximal regions and to facilitate flow in an boral direction
- proximal parts of the stomach and gallbladder also exhibit tonic contractions |
|
|
Term
|
Definition
- moving ring of contraction that propels material along GI tract
- neurally mediated
- in pharynx, esophagus, antrum, small and large intestine
- used to propel chyme in oral to anal direction and consists of both contraction above and relaxation below chyme |
|
|
Term
| Segmentation contractions |
|
Definition
- produce narrow areas of contracted segments interspersed with relaxed segments
- do not cause net forward progression of luminal contents
- most common in sm intestine where it mixes the contents with secretions of the intestines to increase contact of chyme with absorptive linings
- several simultaneous contractions happening cms apart, makes the gut look like chain of sausages
- occur at frequency of slow waves (~12/min in duodenum) |
|
|
Term
| Where do secretions in the digestive tract come from? |
|
Definition
1. salivary glands
2. gastric mucosa
3. pancreas
4. liver and intestinal mucosa |
|
|
Term
| Secretions of the digestive tract |
|
Definition
1. water
2. electrolytes
3. digestive enzymes
4. protein and gut hormones |
|
|
Term
| What initiates secretion in GI tract? |
|
Definition
- multiple signals from the meal, including chemical, osmotic and mechanical components
- elicited by specific effector substances called secretagogues |
|
|
Term
|
Definition
- act on secretory cells to initiate secretion
- act via 3 regulatory mechanisms:
1. endocrine
2. paracrine
3. neurocrine |
|
|
Term
| Exocrine glands in GI tract |
|
Definition
1. acinar: salivary, esophageal, duodenal, and pancreatic
2. tubular: epithelial lining of GI tract from stomach to rectum |
|
|
Term
| General components of secretions |
|
Definition
1. water: aids in passage of meal and provides aqueous medium for enzymes to solubilize nutrients for absorption
2. Inorganic compounds: organ/gland specific - electrolytes, protons, and bicarbonate ions (like acid in stomach and bicarb in duodenum)
3. Organ components: gland or organ specific - enzymes (for digestion), mucin (for lubrication and mucosal protection), endocrine and paracrine molecules, and others like growth factors |
|
|
Term
| Retroperitoneal structures |
|
Definition
| - located posterior to peritoneum and are called primary or secondary depending on where they originated |
|
|
Term
| Primary retroperitoneal structures |
|
Definition
- developed embryologically in subserous fascia on posterior wall of the abdominal cavity and were never suspended in mesenteries
Include:
1. kidneys
2. ureters
3. adrenal glands
4. aorta
5. inferior vena cava
6. cisterna chyli |
|
|
Term
| Secondarily retroperitoneal |
|
Definition
- Originally susepended in mesenteries and became retroperitoneal as a result of crowding in the abdomen due to rotation of the gut
Include:
1. pancreas
2. second, third, and fourth parts of duodenum
3. ascending and descending colon |
|
|
Term
|
Definition
1. forms completely closed sac except in fmeales where uterine tubes open into it
2. Immediately external to it there is an extraperitoneal fatty layer, subserous fascia, and in this layer the organs and their cessels develop and lie
3. If organ remains behind sac (retroperitoneal) it is merely covered ant. with parietal peritoneum |
|
|
Term
|
Definition
| - formed by impressions from inferior epigastric arteries |
|
|
Term
|
Definition
2 that pass from internal iliac artery to the umbilicus
- carry blood to placenta to be oxygenated
- inadult these are obliterated and fibrosed to become the medial umbilical ligaments which form raised folds in peritoneum |
|
|
Term
|
Definition
- portion of the allantois
- in adult it is represented by a fibrous remnant called the median umbilical ligament which connects the apex of the bladder to the umbilicus
- forms median umbilical fold |
|
|
Term
|
Definition
- in fetus it passes superiorly and posteriorly from umbilicus to liver
- occupies lower free border of falciform ligament
- carries oxy blood from placenta to baby liver
- shunted from left portal vein in liver through ductus venosus right into inf. vena cava
- in adults the remnant is the round ligament of the liver |
|
|
Term
|
Definition
- ductus venosus remnant in adults
- can be found in fissure located between the caudate lobe and the left lobe of the liver |
|
|
Term
|
Definition
- pain from organs or from visceral peritoneum covering them is visceral pain
- varies from dull to severe, poorly localized
- carried through visceral sensory fibers in autonomic nerves |
|
|
Term
|
Definition
| - referred to same part of the external body that overlaid the primitive gut during development |
|
|
Term
| foregut derivatives referred pain |
|
Definition
- stomach, pancreas, liver, gallbladder, duodenum
- pain radiates to epigastric region |
|
|
Term
| Midgut derivatives referred pain |
|
Definition
- jejunum, ileum, cecum, appendix, ascending and transverse colon
- radiates to periumbilical region |
|
|
Term
| hindgut derivatives referred pain |
|
Definition
- from descending colon, sigmoid colon and rectum
- radiates to suprapubic (hypogastric) region of anterior abdominal wall |
|
|
Term
|
Definition
- from parietal peritoneum and abdominal wall
- usually acute and well localized because it is carried through typical spinal nerves |
|
|
Term
|
Definition
- during development of upper part of GI tract the stomach is suspended in abdomen by this
- consists of peritoneum and vessels, nerves, lymphatics, and subserous fascia
- spleen develops in dorsal and divides into spleorenal ligamnet between spleen and kidney and a gastosplenic ligament between stomach and spleen
- part becomes very long and overhangs transverse colon and becomes greater omentum |
|
|
Term
|
Definition
- During development of upper GI tract the stomach is suspended in abdomen by this
- liver develops here separating it into the lesser omentum which connects the stomach and liver and the falciform ligament which connects the liver to the anterior body wall
- does not persist caudally |
|
|
Term
|
Definition
has 3:
1. gastrocolic ligament
2. gastrosplenic ligament
3. gastrophrenic ligament |
|
|
Term
|
Definition
- causes peritoneal cavity to be divided into 2 regions: greater and lesser sac (omental bursa)
- when enter peritoneal cavity through anterior wall you are in greater sac
- potential space between parietal and visceral peritoneum surrounds most of the abdominal organs
- if you push your finger post. to hepatoduodenal ligament (of lesser omentum) through epiploic (omental) foramen (of winslow) you will enter the lesser sac (post to stomach and omentum)
- 2 regions to lesser sac: upper recess (behind liver and lesser omentum)and the lower recess (below stomach) |
|
|
Term
|
Definition
- reservoir distal to esophagus which holds ingested food awaiting digestion and absorption in the intestines
- normally in LUQ of abdomen but is highly variable in size, shape, and position, usually not palpable
- most constant landmark is the pyloric sphincter which is only slightly moveable becuase of its attachment to the duodenum |
|
|
Term
|
Definition
1. cardiac: region around junction with esophagus
2. Fundus: dilation superior to the opening of the esophagus that usually rests agains the left dome of the diaphragm
3. Body: major central portion of stomach
4. pylorus: thickened distal portion
- angular notch separates the body from the pylorus, found on the lesser curvature
2 parts to pylorus:
a. antrum: just distal to angular notch
b. pyloric canal: thickened, more distal portion, passage between antrum and pyloric sphincter |
|
|
Term
|
Definition
- of stomach
- prevents regurg of gastric contents sup. into esophagus
- usual site of gastroesophageal reflux disease (GERD) |
|
|
Term
|
Definition
- controls passage of material into duodenum
- distinct thickening of circular layer of smooth muscle at L1 |
|
|
Term
|
Definition
Greater: on inferior aspect of stomach
Lesser: on sup. aspect of stomach |
|
|
Term
|
Definition
Arteries: directly or indirectly derived from celiac trunk:
1. left and right gastrics
2. left and right gastroepiploics
3. short gastric arteries
Veins: parallel arteries in name for most part but tend to be more variable
- venous drainage passes through liver through portal system prior to reaching general circulation
1. left gastric vein: drains area of lesser curvature prior to entering portal circulation
2. esophageal veins: received by let gastric, subject to rupture during portal hypertension |
|
|
Term
| Spleen physical Characteristics |
|
Definition
- varies in size and shape
- usually cannot be palpated since it lies deep to the left 9th, 10th, 11th ribs
- long axis parallel to 10th rib |
|
|
Term
|
Definition
1. stomach
2. pancreas
3. left kidney
4. diaphragm |
|
|
Term
| Vascular supply to spleen |
|
Definition
1. splenic artery from celiac trunk
2. splenic vein joins with sup. mesenteric vein to form the portal vein |
|
|
Term
| What do epithelial cells release in GI tract? |
|
Definition
- Water
- Enzymes
- Mucus
- Acid (in stomach) |
|
|
Term
| Accessory organs of GI tract |
|
Definition
- Pancreas
- Liver
- gallbladder |
|
|
Term
|
Definition
1. Mucosa
2. Submucosa
3. Muscularis externa
4. Serosa (or adventitia) |
|
|
Term
|
Definition
1. Epithelium lining lumen
2. Lamina propria (loose CT)
3. Muscularis mucosa (contractions affect folding of epithelial surface ridges called rugae and pleicae |
|
|
Term
| Epithelial lining of oral cavity, pharynx, and esophagus |
|
Definition
| - non-keratinized stratified squamous |
|
|
Term
| Epithelium of stomach and intestines |
|
Definition
- Simple columnar with goblet cells
- Also contain enteroendocrine cells, which secrete various signaling molecules that activate digestive reflexes |
|
|
Term
| Purpose of folds in GI tract |
|
Definition
1. Increase SA to facilitate absorption
2. Permit expansion of lumen to accommodate a meal
3. Restrict movement of luminal contents |
|
|
Term
| Cancer treatment and GI tract |
|
Definition
- Target mitotic cells
- Normal replacement of epithelial cells does not occur
- Damage can lead to decreased absorption and ulceration
- Also high concentrations of serotonin are dumped from damaged enteroendocrine cells leading to over-stimulation of afferent nerves |
|
|
Term
| Submucosal layer characteristics |
|
Definition
- Rich in CT
- Rich in blood vessels and lymphatics
- Hosues ganglionated plexus of nerves called submucosal plexus (meissner's plexus) |
|
|
Term
|
Definition
- Double layer of smooth muscle (inner circular, outer longitudinal)
- For mechanical processing and propagation of luminal contents of the bowel
- Auerbach's plexus is between the 2 layers and regulates the actions of the muscles
- Circular: constricts
- Longitudinal: shortens |
|
|
Term
| Pseudoobstruction of the GI tract |
|
Definition
- Myenteric plexus inhibits smooth muscle much of the time
- If missing (such as hirchsprung's disease or autoimmune neuropathy) the region of gut constricts
- Leads to this condition because luminal contents are backed up as though there is an obstruction preventing it from passing. |
|
|
Term
|
Definition
- In peritoneal cavity structures of digestive tract are covered with this sheet-like serous membrane comprised of a monolayer of mesothelial cells
- Same as visceral peritoneum |
|
|
Term
|
Definition
- Dense network of collagen fibers
- Envelops GI structures that are retroperitoneal (most of duodenum, ascending colon, descending colon, rectum) as well as upper regions of GI tract from oral cavity to esophagus
- Attaches these regions to adjacent structures |
|
|
Term
| Upper esophageal sphincter |
|
Definition
- region of increased tone in esophagus
- restricts flow of air into esophagus |
|
|
Term
| Lower esophageal sphincter |
|
Definition
- region of increased tonicity
- prevents reflux of acidic gastric contents into esophagus
- "physiologic sphincter" since there are no gross anatomical or histological features of sphincter (like thickened circular muscle layer) |
|
|
Term
|
Definition
- in submucosa of esophagus
- produce mucous secretion that lubricates mucosal lining and facilitates the passage of food toward the stomach |
|
|
Term
| Muscularis externa of esophagus |
|
Definition
1. upper 1/3 is striated
2. middle 1/3 is mixed
3. lower 1/3 is smooth |
|
|
Term
|
Definition
| - mixture of fluids, partially digested food particles, and enzymes in stomach - has consistency of thick soup |
|
|
Term
| Primary function of the stomach |
|
Definition
- regulates rate at which chyme enters small intestines where most of the process of digestion and absorption takes place
- in absence of a stomach a normal-sized meal moves so rapidly through small intestines that only a fraction of food can be digested/absorbed
- why gastric bypass is considered a treatment for morbid obesity |
|
|
Term
| Four divisions of stomach |
|
Definition
1. cardia: where esophagus meets stomach
2. fundus: above entry of esophagus, rests against diaphragm and usually has air bubble
3. body: largest part of stomach between fundus and pyloric antrum
4. antrum: region beyond incisura angularis that leads to outlet of stomach (pyloric sphincter) |
|
|
Term
|
Definition
- contains thick layer of circular muscle that gives it a sphincter function
- prevents chyme from leaving stomach before it is ready |
|
|
Term
| Functional divisions of stomach |
|
Definition
1. proximal region consisting of fundus and corpus which serves as storage resevoir for a recently digested meal
2. distal antral pump region that consists of the antrum and part of the corpus, serves to mix gastric contents and propel chyme through pylorus and into duodenum |
|
|
Term
|
Definition
| - connects lesser curvature of stomach to the liver, attached to lesser curvature |
|
|
Term
| Greater curvature attachments |
|
Definition
1. gastrophrenic ligament: stomach to diaphragm
2. gastrosplenic ligament: stomach to spleen
3. greater omentum: large apron-like sheet of peritoneum that passes from here and covers most of small and large intestines
4. gastrocolic ligament: lies between stomach and transverse colon - part of greater omentum |
|
|
Term
|
Definition
- temporary longitudinal folds in mucous membrane inside stomach
- allows for distention after eating a meal |
|
|
Term
|
Definition
- invaginations in the simple columnar epithelium of the stomach
- increase surface area of the epithelium
- mucous cells along walls of pits release alkaline mucus secretion that coats and protects epithelial lining from acidic gastric contents
- gastric glands feed into gastric pits at the interface is where stem cells of stomach are |
|
|
Term
| Histological divisions of stomach |
|
Definition
1. cardiac: contains tubular glands with mucus-secreting cells and shallow pits
2. fundus: also includes body
3. pyloric regions: also includes antrum |
|
|
Term
|
Definition
- extend deep into lamina propria
comprised of 2 cell types:
1. parietal cells
2. chief cells
3 regions
1. isthmus: surface mucus and parietal cells
2. neck: neck mucus cells and parietal cells
3. base (peptic/chief and parietal cells)
- endocrine cells scattered throughout glands |
|
|
Term
| pyloric or antral/pyloric glands |
|
Definition
- mucosal tubular glands in antral and pyloric regions
- produce primarily mucous secretion rather than enzyme-rich acidic secretion that occurs in the fundus and corpus
- relatively rich in enteroendocrine cells crucial for regulation of gastric secretions and motility (like the G cells and D cells) |
|
|
Term
|
Definition
- secretes gastrin which acts via blood stream to trigger parietal and chief cell secretions as well as gastric motility
- found throuhgout stomach but most numerous in antrum and pylorus |
|
|
Term
|
Definition
- found in pylorus
- secretes somatostatin, which acts on neighboring G cells (mainly through negative feedback paracrine mechanism) to decrease gastrin production and secretion |
|
|
Term
| Small intestine and surface area |
|
Definition
- duodenum, jejunum, ileum
1. mucosal folds: 2-3 fold increase in SA
2. villi: 10 fold increase in SA
3. Microvilli: 20-30 fold increase in SA |
|
|
Term
| Cells in the epithelium of the small intestine |
|
Definition
1. enterocytes (absorptive cells)
2. goblet cells (mucus)
3. paneth cells
4. stem cells
5. enteroendocrine cells |
|
|
Term
|
Definition
- starts at the distal end of the pylorus and is C shaped
- first part is only part that has a mesentery (hepatoduodenal ligament, which is part of the lesser omentum)
- remainder of duodenum is retroperitoneally located and is continuous with jejunum |
|
|
Term
|
Definition
- area of descending part of duodenum where the common bile duct and pancreatic duct empty
- its location is marked on internal wall of duodenum by a mound called duodenal ampulla
- terminal portion of these ducts are surrounded by a sphincter, sphincter of Oddi within wall of of duodenum |
|
|
Term
| Intestinal glands of duodenum |
|
Definition
| - contain relatively high number of enteroendocrine cells that secrete many important signaling molecules such as cholecystokinin (CCK, secretin, and gastric inhibitory peptide (GIP), which have hormonal actions, and serotonin, which has a paracrine effect on nerves of the lamina propria |
|
|
Term
|
Definition
- submucosal glands of duodenum that allow histological definition
- cells of these glands secrete copious amounts of mucus and bicarbonate which forms a protective barrier and raises the pH of the luminal contents protecting intestinal lining from acidic chyme being delivered from the stomach |
|
|
Term
|
Definition
| - normally, secretions from glands of the duodenum have a strong buffering capacity, however, imbalances between amount of acid in the chyme and buffering capacity of the tissue, ulcers can form |
|
|
Term
|
Definition
- bilayered sheet of peritoneum
- on body wall, the root of mesentery extends from the left of the vertebral column at the level of the duodeno-jejunal junction inferiorly to the region of the right iliac fossa
- root is only 6 inches long but it fans out over the 20 feet of intestine
- blood vessles and nerves that supply small intestines pass through here between its too sheets of peritoneum |
|
|
Term
|
Definition
- folds htat lie perpendicular to the long axis of the bowel in small intestine
- more prominent in jejunum than ileum |
|
|
Term
|
Definition
- somewhat thinner wall
- less prominent mucosal folds
- Peyer's patches (also in jejunum)
- jejunum is thicker and has mesentary which is less fatty and has fewer arcade branches of the superior mesenteric artery |
|
|
Term
| Stem cells of crypts and differentiation |
|
Definition
- toward base of crypts
- one daughter cell from each division is maintained as stem cell
- other daughter cell can become enterocyte, enteroendocrine cell, goblet cell or paneth cell
- cells in enterocyte lineage divide several more times as they migrate up along the crypts and onto villi (where they differentiate into mature absorptive cells that express all of the transport proteins and enzymes characteristic of those cells |
|
|
Term
| Response to a meal phases |
|
Definition
1. cephalic
2. oral
3. esophageal
4. gastric
5. duodenal and intestinal
- in each phase the components of the meal present certain stimuli that activate different pathways resultingin changes in effector function |
|
|
Term
| Cephalic phase of digestion |
|
Definition
- main feature is activation of GI tract for meal
Stimuli:
1. cognitive
2. olfactory
3. visual
4. auditory
Pathways:
- all stimuli result in increase in excitatory parasympatheric outflow to the enteric nervous system
Effectors: increase in parasympathetic outflow results in:
1. increased salivary secretion
2. increased gastric acid secretion
3. increased pancreatic enzyme secretion
4. gallbladder contraction
5. relaxation of sphincter of Oddi |
|
|
Term
|
Definition
- main features are mechaincal disruption of food and initiation of digestion
- chewing subdivides and mixes food with
1. salivary amylase
2. lingual lipase
3. mucin (lubricates food for chewing and swallowing)
- minimal absorption in mouth although alcohol and some drugs are absorbed (clinically relevant)
- the stimuli, pathways, and effectors are the same as cephalic but in addition there are stimuli generated from the mouth that are mechanical and chemical (taste) |
|
|
Term
|
Definition
Main functions of saliva:
1. lubrication and moistening of food for swallowing
2. solubilization of material for taste
3. antibacterial action
4. initiation of starch digestion
5. clearance and neutralization of the esophagus of refluxed gastric secretions |
|
|
Term
| Functional anatomy of salivary glands |
|
Definition
3 pairs of major glands:
1. parotid
2. mandibular
3. sublingual
- smaller on lip, tongue and palate (acinar glands)
- parotid is mainly serous and sublingual is mucus, submandibular is mixed |
|
|
Term
|
Definition
- unique properties of saliva are: large volume relative to mass of gland
- low osmolarity
- high potassium concentration
- specific organic constituents |
|
|
Term
| Inorganic componentes in saliva |
|
Definition
| - Composition is entirely dependent upon the gland, the stimulus and the rate of salivary flow. The major components are electrolytes and bicarbonate |
|
|
Term
| Organic components in saliva |
|
Definition
- proteins and glycoproteins are synthesized, stored, and secreted by acinar cells
- major products are: amylase, lipase, glucoprotein, and lysozyme (attacks bacterial cell wallls)
- the duct cells produce various growth factors important for the maintenance of the GI tract |
|
|
Term
| Regulation of salivary secretion |
|
Definition
- exclusively neural
- stimulated by both sympathetic and parasympathetic subdivisions of the autonomic nervous system
- parasympathetic is much more important in response to a meal
- innervation is facial and glossopharyngeal to both acinar and duct cells
- parasymp stimulation (cholinergic) produces high rates of flow via activation of transport processes, an increase in blood flow and myoepithelial cell contraction |
|
|
Term
|
Definition
- act of swallowing
- sequential, well-coordinated series of events that propels a bolus of food from the oral cavity to the pharynx and from there to the stomach
- begins voluntarily and ends involuntarily
- Swallowing center in the brainstem |
|
|
Term
| Involuntary phase of swallowing reflex |
|
Definition
- begins in pharynx when sensory nerve endings detect a bolus of food
- breathing stops momentarily and then the soft palate is elevated to prevent food from entering internal openings of nostrils
- impulses from receptors pass along the glossopharyngeal nerve, sup. laryngeal branch of vagus, and maxillary division of trigeminal |
|
|
Term
| Esophageal phase of digestion |
|
Definition
- esophagus and its associated structures have 2 main functions both of which are motor:
1. transfer food to stomach
2. protective functions (protect esophagus from acidic gastric secretions and airway protection)
Stimuli: mechanical: pharyngeal stimulation during swallowing and esophageal distension
Pathways: mechanosensitive afferents in both extrinsic nerves and intrisic neural pathways respond to esophageal distension
- pathways include: activated reflex pathways via brainstem (extrinsic, vagus) or solely intrinsic pathways (enteric nervous system)
- striated muscle is fregulated from the nucleus ambiguus in the brainstem
- smooth muscle is regulated by parasympatheric outflow via the vagus nerve and by intrinsic nerves
Effectors: changes in function that result in food being in the esophagus:
1. striated and smooth muscle peristalsis
2. relaxation of the lower esophageal sphincter (LES)
3. relaxation of proximal stomach |
|
|
Term
| Motor activity during the esophageal phase |
|
Definition
- the UES, esophagus, and LES act in a coordinated manner to propel material along the esophagus from the pharynx to the stomach
- bolus passes through UES and initiates a peristaltic wave along the esophagus called PRIMARY peristalsis (moves down the esophagus slowly and before it reaches the sphincter the LES relaxes)
- distension of the esophagus by the bolus initiates another wave called SECONDARY peristalsis
- often repetitive secondary peristalsis is required to clear the esophagus
- in addition, esophageal distension produces receptive relaxation of the stomach
- proximal stomach relaxes at the same time as the LES, this occurs with each swallow and its functionis to allow the stomach to accommodate large volumes with a minimal increase in intragastric pressure |
|
|
Term
|
Definition
| - initiated by distention of the esophagus by a bolus |
|
|
Term
|
Definition
- passage of bolus through UES initiates this wave
- moves down esophagus slowly (3-5 cm/sec) |
|
|
Term
|
Definition
- condition in which a bolus of food passes relatively slowly along the esophagus and its arrival at the lower end of the esophagus does not initiate a reflex-induced relaxation of LES, causing accumulation in lumen of the esophagus
- Due to degeneration of neurons in the region of the LES and serum usually contains anti-neuronal anitbodies
Treatment:
- making cuts in circular muscle in region of the LES or expanding a balloon in this region to cause tearing of the muscle and decreased tone
- another therapy is injection of botulinum toxin into LES to disrupt excitatory neural input to the smooth muscle, thus decreasing tone |
|
|
Term
|
Definition
- gastroesophageal reflux disease: when tone of LES is decreased due to physical changes or certain foods such as caffeine, alcohol, or chocolate, reflux of gastric contents into the esophagus can occur
- acids make the epithelial erosion and local inflammation results (esophagitis)
- chronic GERD can lead to Barrett's esophagus in which the epithelium converts from stratified squamous to simple columnar could lead to esophageal cnacer |
|
|
Term
| Gastric Phase of digestion |
|
Definition
Stomach has many functions:
1) storage - temporary reservoir for meal
2) secretes H+ to kill microorganisms and to convert pepsinogen to active form
3) secretion of intrinsic factor to absorb vitamin B12 (cobalamin)
4) secretion of mucus and bicarbonate to protect the gastric lining
5) secretion of water for lubrication and to provide aqueous suspension of nutrients and
make them hypoosmotic
6) motor activity to mix secretions
7) coordinated motor activity to regulate emptying of contents into duodenum
Stimuli:mechanical (distension/stretch of smooth muscle wall),
chemical (oligopeptides and amino acids in the lumen)
Pathways:
- Neural: there are both intrinsic and extrinsic neural reflex pathways that are important for the regulation of gastric functionAfferent neurons that pass from the GI tract to the CNS via the vagus
nerve (and to a lesser extent to the spinal cord) respond to mechanical and chemical stimuli and
activate parasympathetic outflow that is both excitatory and inhibitory.
Endocrine: These pathways include the release of gastrin that stimulates gastric secretion, and the
EFFECTORS:
Secretory responses include
acid secretion
• pepsinogen secretion
• mucus
• intrinsic factor
• gastrin
• lipase
• bicarbonate
Motor Responses (changes in activity of smooth muscle activity):
• inhibition of the proximal stomach motility (receptive relaxation),
• stimulation of distal stomach motility causing antral peristalsis (antral pump).
release of somatostatin that inhibits gastric secretion.
Paracrine: These pathways include histamine release to stimulate gastric acid secretion. |
|
|
Term
|
Definition
- The predominant secretion from the stomach is H+. This occurs in the face of a huge concentration gradient and is a very energy intensive process.
- The major function of acid is
conversion of inactive pepsinogen (the major enzyme product of the stomach) to pepsin, which initiates protein digestion in the stomach.
- Acid may also be important for prevention of the invasion and colonization of the gut by bacteria and other pathogens.
- The stomach also secretes significant
amounts of bicarbonate and mucous that is important for mucosal protection. *** The only required gastric secretion, and for that matter, the only vital function of the stomach, is the secretion of intrinsic factor by parietal cells, which is required for the absorption of vitamin B12
(cobalamin). |
|
|
Term
| Inorganic Composition of gastric secretions |
|
Definition
Inorganic: The predominant inorganic component of gastric secretions is H+. The composition of
gastric juice is dependent on the rate of secretion; with increases in the rate of secretion H+ increases,
K+ is always higher than plasma, and Cl- is the major anion. |
|
|
Term
|
Definition
- H+ secreting cell and it has a remarkable structure-function relationship
- cells are pyramidal in shape and at the base the sides bulge into lamina propriaThe cells
are densely acidophilic due to large and densely packed mitochondria. A tubulovesicular apparatus
and intracellular canaliculi appear at the EM level. There are microvilli on the canaliculi, which are
long and face the gastric lumen. These structures serve to increase the surface area for secretion.
When the cell is stimulated to secrete, the tubules and vesicles fuse with the plasma membrane
resulting in a dramatic increase in the surface of the cell that faces the lumen and a very efficient
pumping of H+. |
|
|
Term
| Cellular mechanism of proton secretion from parietal cells |
|
Definition
- H+ is pumped against a huge concentration gradient (1 million: 1).
- The apical membrane contains a primary
primary proton pump, an H+/K+ATPase that exchanges H+ for
K+.
- Chloride ions are secreted into the lumen through chloride channels. The source of the H+ ions is metabolism and activity of carbonic anhydrase.
- The bicarbonate ions that are
formed are transported out of the basolateral side of the parietal cells, thereby maintaining normal intracellular pH. |
|
|
Term
| Organic components of gastric secretion |
|
Definition
- Pepsinogen is secreted from chief cells as an inactive proenzyme. Pepsinogen is converted to pepsin (the active form of the enzyme) in the acidic environment of gastric lumen. Pepsin then acts further on pepsinogen to generate more active enzyme.
- Mucus secreted in the stomach forms a gel with water and bicarbonate ions. This gel provides a gastric mucosal barrier that protects the gastric mucosa from damage induced by acid and pepsin. |
|
|
Term
| Mucus and Bicarbonate secretion in stomach |
|
Definition
- from mucous neck cell in stomach
- Tonic secretion in response to irritation of mucosa
- provides a physical barrier between lumen and epithelium |
|
|
Term
| Intrinsic factor and gastric acid (HCl) release in stomach |
|
Definition
- from parietal cells
- release stimulated by ACh, gastrin, and histamine
- it activates pepsin, kills bacteria
- complexes with vitamin B12 to permit absorption |
|
|
Term
| Histamine release in stomach |
|
Definition
- by enterochromaffin-like cells
- release stimulated by Ach and hastrin
- stimulates gastric acid secretion |
|
|
Term
| Pepsinogen and gastric lipase release in stomach |
|
Definition
- by chief cells
- in response to Ach, acid, secretin
- digests protein (pepsin) and digests fat (gastric lipase) |
|
|
Term
| Parietal cell and gastric acid release |
|
Definition
- initiated most strongly by parasympathetic innervation via reflexes involving the vagus nerve
- efferent fibers end on intrinsic neurons that innervate parietal cell, enterochromaggin-like cells and endocrine G cells
- release of Ach directly stimulates the parietal cell
- parasymp also releases gastrin via the blood stream and histamine via local diffusion that stimulate patietal cell |
|
|
Term
|
Definition
- superficial breakdowns of GI lining, not involving mucosa
- generally heal without scars |
|
|
Term
|
Definition
- breakdowns of the GI lining involving muscularis and deeper layers
- complications include pain, bleeding, perforations, obstructions and death
- ulcers generally due to imbalance between mucosal aggressive factors and mucosal resistance factors |
|
|
Term
|
Definition
| - used to describe one or more ulcers involving stomach or duodenum in the absence of a gastric or small-intestinal malgnancy |
|
|
Term
| Mucosal aggressive factors |
|
Definition
- acid (H+) can be considered an aggressive factore, but the healthy stomach duodenum has ample natural protection agai nst the destructive effects of acid
Factors that magnify effects:
1. pepsin
2. bile
3. helicobactor pylori
4. NSAIDs (non-steroidal anti-inflammatory drugs)
Risk factors:
1. alcohol
2. tobacco
3. caffeine |
|
|
Term
| Mucosal resistance (gastric) |
|
Definition
- sometimes collectively "gastric mucosal barrier"
- gastric epithelium with tight junctions provides tight resistance to backflux of luminal H+
- mucus: secreted by cells in spithelium in response to Ach, prostaglandins and mechanical stim of mucosa
- bicarbonate ions: along with mucus these from a gel zone above the gastric epithelium that traps luminal H+ that approach from mucosa and neutralizes them |
|
|
Term
| Therapeutic approaches to reduce H+ secretiona nd raise gastric lumen pH |
|
Definition
- antacids
- H2 histamine receptor blockers
- proton pump inhibitors
ALL to decrease symptoms of acid reflux by raising pH of luminal contents |
|
|
Term
|
Definition
- Bacterium
- factor that can lead to gastritis, ulcer formation and gastric carcinoma.
- can exist in the stomach because it secretes an enzyme, urease, which converts urea to NH3, and is used to buffer H+ by forming NH4+. An aggressive regimen of antibiotic treatment, typically in combination with an H+, K+-ATPase (proton pump) inhibitor, can often eliminate the infection, after which the gastritis and ulcer symptoms resolve. |
|
|
Term
| Activation and action of chief cells |
|
Definition
- secretion initiated by presence of acid in stomach (H+ causes release of Ach)
- vagal input to stomach can also activate enteric neurons that stim chief cells during cephalic, oral, and gastric phases
- exocytosis of contents of zymogenic granules leads to the release of pepsinogen and lipase
H+ converts pepsinogen to pepsin, which acts to convert pepsinogen to pepsin |
|
|
Term
| Gastric motility main functions |
|
Definition
1. provide resevoir for ingested food
2. produce fragmentation of food and mixing with secretions
3. regulate emptying of contents into duodenum at controlled rates |
|
|
Term
| Proximal stomach function |
|
Definition
- fundus/body
- produces slow changes in tone compatible with its reservoir
function.
- important for receiving and storing
food, and for mixing of the contents with gastric juice.
- Generation of tone in the proximal stomach is also an important driving force in the regulation of gastric emptying. |
|
|
Term
| Effect of low stomach tone |
|
Definition
- causes low intragastric pressure
- associated wtih delayed or slow gastric emptying and an increase in tone in the proximal region is required for gastric emptying to occur |
|
|
Term
|
Definition
- antrum/pylorus
- important for the mixing of gastric contents and propulsion of chyme through the pylorus and into the duodenum.
- The antrum produces strong, phasic contractions at a rate of about 3-5/min. Contractions generated by the
slow waves begin in mid-stomach and progress towards the pyloric sphincter.
- In the gastric phase of the meal, the pyloric sphincter is usually closed, and
these antral contractions serve to mix gastric contents, which results in mixing and the reduction in the size of solid particles (grinding).
- during gastric emptying, these antral contractions are important for the propulsion of the gastric contents
contents through the pyloric sphincter and into the duodenum |
|
|
Term
|
Definition
- at gastro-duodenal junction
- region of high pressure generated by tonic smooth muscle contraction
- it is important in regulation of gastric emptying
- strong antral contractions lead to pyloric opening allowing gastric emptying to occur |
|
|
Term
| Control of gastric motility (stimuli, pathway, effectors) |
|
Definition
S: both mechanical and chemical
- distension
- presence of products of protein digestion (amino acids and small peptides)
P: vaso-vagal reflexes include extrinsic vagal afferents: fibers that terminate in the muscle and mucosa
- mucosal afferents respond to chemical stimuli and mechanosensitive afferents respond to distension and contraction of smooth muscle
- this afferent stimulation results in relfex activation of vagal efferent (parasymp) outflow
E: inhibition: of smooth muscle in the proximal stomach to cause reflex receptive relaxtion
Activation: of smooth muscle in the distal stomach to produce and strengthen antral contractions |
|
|
Term
|
Definition
- control center of sorts for the digestive process
- flow of gastric contents into the duodenum activates a series of events that facilitate digestion of luminal contents along the length of the small intestine. This involves regulating the delivery of chyme from the stomach
to match the digestive and absorptive capacity of intestine.
- The duodenum also is the site where
pancreatic juices and bile, which are crucial for the digestive process, enter the intestines.
- Therefore, the function of this region is highly associated with feedback mechanisms that control the rate of gastric emptying, and regulatory signals that activate pancreatic section and bile flow. |
|
|
Term
| Stimuli for duodenum function |
|
Definition
1. distension
2. protons
3. changes in osmolarity
4. nutrients |
|
|
Term
| Pathway for duodenal activation |
|
Definition
Neural pathways
1. spinal
2. vagal
3. intrinsic reflexes
Hormonal pathways:
1. cholecystokinin (CCK)
2. secretin
3. GIP
Paracrine actionsL include effects of CCK and serotonin on afferent nerve fibers in the lamina propria |
|
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Term
| Effects of duodenal function |
|
Definition
1. increase pancreatic secretion
2. increase in gallbladder contraction
3. relaxation of sphincter of Oddi
4. regulation of gastric emptying
5. inhibition of gastric acid secretion
6. interruption of MMC (migrating myoelectric complex) |
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Term
| Intestinal feedback inhibition of gastric emptying |
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Definition
| activation of vagal efferent outflow will decrease antral contractions, contract the pylorus and decrease proximal gastric motility resulting in feeback inhibition |
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Term
|
Definition
- liquids empty rapidly and solids empty only after a lag phase
- regulation occurs by alterations in motility of the proximal and distal stomach, pylorus and duodenum
- emptying brought about by increase in tone (intralumenal pressure) in proximal stomach and increase in strength of antral contractions, opening of the pylorus and inhibition of duodenal segmental contractions |
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Term
| Total body fluid primary divisions |
|
Definition
2/3 intracellular fluid
1/3 extracellular fluid: high [Na] isotonic saline |
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Term
|
Definition
- high [K] isotonic saline
2/3 of total body fluid (TBF) |
|
|
Term
| Extracellular fluid primary divisions |
|
Definition
1. interstitial fluid (3/4)
2. plasma volume (1/4): 93% aqueous saline and 7% solid material |
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Term
|
Definition
1. Plasma protein and lipid = 7%
2. plasma fluid (Na-saline) = 93% |
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Term
|
Definition
- really means total H2O molecules (if extracted how much would they weigh)
- no free water in the body, only isotonic saline
- 60% of total body weight
- Total body water (TBW) can be estimated by the dilution of a test solute (or radioisotope) into total body fluid |
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|
Term
| Distribution of free water added to the body |
|
Definition
2/3 to intracellular fluid
1/3 extracellular |
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Term
| Adding saline to the body |
|
Definition
all will go to the ECF because there is no net driving force sending fluid from ECF to ICF
- increases total body aqueous solution by 1000 mL NO EFFECT on total body water |
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|
Term
| Adding 5% dextrose solution to the body |
|
Definition
- 2/3 to ICF
- 1/3 to ECF
- increases total body free water from 0 - 1000 mL |
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|
Term
| addition of isotonic saline vs free water to the body |
|
Definition
1. addition of aqueous isotonic Na-saline will expand the ECF and TB-IS
2. addition of free water will dilute the isotonic saline in both the ECF and ICF without adding to TB-IS so the free water will be excreted by the kidney |
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Term
|
Definition
|
|
Term
|
Definition
|
|
Term
|
Definition
1. first space = ICF
2. second space = ECF with interstitial fluid and intravascular fluid. Intravascular space can only be expanded with whole blood to increase plasma and circulating blood cells
3. potential space (pleural, peritoneal, synovial spaces) contains a small amount of fluid and collection here is abnormal and usually can only be drained by a needle |
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Term
| Water balance and tonicity |
|
Definition
- net free water content of the body is zero in the steady stateL rate of free water ingestion = excretion
- ingestions is regulated by thirst stimulated by water loss
- excretion of water is regulated by kidney under hormonal control by ADH (secreted by post. pituitary) |
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Term
|
Definition
- makes the cell swell
- water moves down concentration gradient into the hypertonic cell |
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Term
|
Definition
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|
Term
| intracellular volume regulation |
|
Definition
- tonicity (net water balance)
- cannot be assessed by physical examination
- can only usually be assessed by obtaining the plasma concentration of effective osmoles |
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|
Term
| Extracellular volume regulation and assessment |
|
Definition
- regulated by the content of isotonic Na-saline
- can be assessed on physical examination |
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|
Term
|
Definition
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|
Term
| Renal handling of free water |
|
Definition
- nephron beyond the proximal tubule (loop of Henle and distal nephron) and the ADH-sensitive collecting duct act as the water-regulating system
- although the proximal tubule plays a major role in the bulk resorption of isotonic NaHCO3 and NaCl it does not significantly affect free water balance |
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Term
|
Definition
| determined by the number of particles in a solution, regardless of whether they are capable of exerting an osmotic force (make water move) across a biological cell membrane |
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Term
|
Definition
| determined by that subset of particles, called effective osmoles, which exert an osmotic force across a biological cell membrane |
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|
Term
| Movement of qater beyond the proximal tubule in the kidney to the medulla |
|
Definition
| - solute and water head from the relatively isotonic renal cortex down the descending limb of Henle toward the hypertonic renal medulla |
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|
Term
|
Definition
- water permeable so water leaves (gets reabsorbed) as it goes down making the urine more hypertonic
- through the process of counter-current multip0lication? |
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|
Term
| Tip of the loop of Henle osmolality |
|
Definition
| - maintained at an effective osmolality of 1200-mosmols/kg (600 from Na+ and Cl- and 600 from urea - an effective osmole in the kidney |
|
|
Term
| What happens in the ascending loop of Henle |
|
Definition
- goes toward the cortex
- water-impermeable, thick loop
- Na+-K+-2Cl- triple co-transporter removes solute from urine so urine becomes more dilute
- the solutes are reabsorbed into the renal interstitium to maintain the hypertonicity of the medulla |
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|
Term
| Final urine concentration depends on.. |
|
Definition
|
|
Term
| Requirements for maximal free water excretion |
|
Definition
1. Deliver adequate filtrate to the concentrating/diluting segments of the nephron - a problem in renal hypoperfusion or insufficiency
2. Intact function of concentrating/diluting segments:
a. ability to separate solute from water to create free water
b. a problem if transport is inhibited by drugs or renal injury
3. ability to maximally suppress ADH effect - a problem with certain durgs and paraneoplastic syndromes |
|
|
Term
| Requirements for maximal free water reabsorption |
|
Definition
1. Deliver adequate filtrate to the concentrating/diluting segments of the nephron - a problem in renal hypoperfusion or insufficiency
2. Intact function of concentrating/diluting segments:
a. ability to separate solute from water to create free water
b. a problem if transport is inhibited by drugs or renal injury
3. Ability to maximally stimulate ADH secretion - a problem if the post. pituitary fails to produce enough (central DI)
4. Normal responsiveness of the ADH-sensitive segments of the distal nephron - a problem if anything is wrong with the V2 receptor, intracellular signal transduction system or trafficking pathways fro the AQP2 water channer, or the AQP2 water channel itself (congenital or acquired nephrogenic DI) |
|
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Term
|
Definition
| - osmole that will cause water to move across a biological membrane because it does not equilibrate across the membrane (like salt ions in ECF and sugar) |
|
|
Term
| Ineffective osmole in ECF |
|
Definition
- Urea
- addition of urea to iostonic saline soltion containing red blood cells will not cause a steady state change in cell volume
- the cell membrane is permeabloe to urea so intracellular urea concnetration will equilibrate with the extracellular urea
- large molecules can also be ignored because they have negligable effects on osmolality and tonicity |
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|
Term
|
Definition
- can also affect osmolality and tonicity
- most common effective is mannitol: a non-metabolizable sugar administered intravenously for the treatment of cerebral edema following head trauma
- most common exogenous ineffective osmole is ethanol |
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|
Term
| osmolality equation in terms of osmoles |
|
Definition
| = endogenous osmoles + exogenous osmoles |
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|
Term
| Tonicity equation in terms of osmoles |
|
Definition
| = endogenous EFFECTIVE osmoles + exogenous EFFECTIVE osmoles |
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|
Term
| Endogenous osmolality esitame |
|
Definition
2*([Na] + [K]) + [glucose]/18 + [BUN]/2.8
2 in the beginning accounts for Na+, Mg2+, and Ca2+ and their anions (does not account for K+ so in estimate 2 K+ is removed)
- glucose/18 is to change the units from mg/dL to mM
- BUN/2.8 is for the same conversion |
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|
Term
|
Definition
- total body hypotonicity is almost always due to retention of free water
- this positive water balance is almost always due to a defect in free water excretion usually associated with elevated levels of ADH
- in some cases, hypotonicity can develop as a result of inadequate solute intake (whih climits free water excretion), excessive water intake (ex: primary polydipsia) or excessive loss of solute (ex: cerebral salt wasting) |
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Term
|
Definition
- almost always due to loss of free water combined with an inability to replace the loss
- frequently seen in institutionalized and hospitalized patients
- up to 60% die |
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|
Term
|
Definition
- inability to sense thirst
- rare |
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|
Term
| Negative water balance (dehydration) and hypertonicity - when they occur |
|
Definition
due to a thirsty person:
1. not being able to get to water
2. not being able to express or act on thirst (unable to speak after stroke for instance)
3. the rate of water loss from GI tract (severe diarrhea) or skin (severe burns) outstrips the rate of water input |
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|
Term
|
Definition
- comprised of a filter (glomerulus) and a tubule that selectively reabsorbs water and sulte from the filtrate as well as secreting some into urine
- we have 1 - 3,000,000 nephrons in our 2 kidneys |
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|
Term
| What drives filtration in nephrons |
|
Definition
- physical forces:
1. pressure
2. pore size |
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|
Term
| What happens to nephrons when aging |
|
Definition
- nephron loss
- remaining nephrons adaptively increase function
- tremendous reserve: one may be asymptomatic with less than 10% of nephron units functioning |
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|
Term
| What happens without nephron function |
|
Definition
| - survival is less than 1-2 weeks |
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|
Term
| How much water, sodium, and urea are reabsorbed into kidney |
|
Definition
|
|
Term
|
Definition
1. excretes toxins generated by metabolism
2. maintains body fluid balance
3. maintains body solute balance
4. secretes 3 hormones:
a. renin
b. erythropoeitin
c. 1-25 (OH)2 vitamin D (calcitriol)
5. Degrades or generates key organic molecules |
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Term
|
Definition
| - end arterial vessels in kidney that terminate in afferent arterioles and glomeruli (specialized capillary tufts)in the renal cortex (where all the glomeruli are) |
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Term
|
Definition
- specialized vascular bundles that dip down into the renal medulla surround long loops of henle and collecting ducts
- anatomic relationships are key for urine concentration and dilution |
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|
Term
| Glomerular capillary tuft |
|
Definition
- unique anatomy: capillary network returns to a muscular arteriole rather than a venous plexus
- thus the pressure within the capillary bed can be controlled by 2 resistances in series
- the efferent arteriole then again feeds a second capillary bed (peritubular capillaries) which in turn epty into the venous system
- this arrangement is critical for regulating filtration of the blood as it traverses the glomerular capillary |
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|
Term
|
Definition
- secreted by granular cells int he juxtaglomerular apparatus in response to either:
1. decrease in pressure int he afferent arteriole
2. decrease in cl uptake by the early distal tubule at the macula densa |
|
|
Term
|
Definition
- key hormone through its effects to activate angiotensin
- plays a key role in increasing a generalized vasoconstriction preferentially in the efferent arteriole and thereby maintaining pressure in the glomerular capillaries to drive filtration in the face of decreased perfusion pressure in the afferent arteriole |
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|
Term
|
Definition
- involved in regulation of vascular tone and directly stimulates renal sodium reabsorption
- also stimulates aldosterone secretion, which in turn regulates sodiuma nd potassium balance
- also appears to play a role in autoregulation, via renin secretion from macula densa signals |
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|
Term
|
Definition
- stability of GFR in the face of variations in systemic blood pressure
- critically important for stability of foltration
- achieved by minute-to-minute adjustments in afferent and efferent arteriolar vasoconstriction
- probably involves stretch-induced release of NO by vascular endothelial cells
- macula densa feedback system may also play a role |
|
|
Term
| Glomerular filtration rate |
|
Definition
- determined largely by hydrostatic pressure gradient across glomerular capillaries
- controlled by autoregulation |
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|
Term
|
Definition
- synthesized and secreted continually by peritubular interstitial cells
- secretion rate increases in response to a fall in O2 tension
- stimulates RBC production in marrow
- anemia of chronic kidney disease is due to erythropoietin deficiency |
|
|
Term
|
Definition
- Proximal tubule epithelial cells contain a key enzyme that forms the active form of vitamin D (1-25 dihydroxy D3) known as calcitriol
- kidney regulates the amount synthesized and secreted in response to signals received from the parathyroid hormone and serum phosphate concentration
- Calcitriol increases gut Ca++ absorption and bone Ca++ release
- decreases parathyroid secretion |
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|
Term
|
Definition
- bony structure which is interposed between the movable vertebral column, which it supports, and the femur
- composed of 4 bones:
1. 2 hip bones
2. sacrum
3. coccyx
- divided in greater (false) and lesser (true) pelvis by an oblique plane passing through the promontory of the sacrum, the arcuate line, the pecten pubis and the sup. margin of the symphysis pubis |
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Term
|
Definition
| circumference of the oblique plane that divides the pelvis into lessera nd greater pelvis |
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|
Term
|
Definition
- superior pelvic aperature
- entire opening surrounded by the pelvic brim |
|
|
Term
|
Definition
- expanded portion of the cavity superior to eht pelvic brim
- bounded on either side by the ilium |
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|
Term
|
Definition
- space between the pelvic inlet and pelvic outlet
- contains the sigmoid colon, rectum, bladder, uterus, or prostate and associated reproductive structures
- recutm is located in the curve of the sacrum and coccyx and the bladder is against the dorsal surface of the pubic symphysis
- in female, the uterus and vagina occupy the interval between these viscera |
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|
Term
|
Definition
- inferior pelvic aperature
- bounded by coccyx, the ischial tuberosities, the ischiopubic rami and pubic symphysis
- greater and lesser sciatic notches are separated by te ischial spine and are transformed into greater and lesser sciatic foramina by the sacrospinous and sacrotuberous ligaments |
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|
Term
|
Definition
| - in the erect posture, the position of the pelvis may be indicated by holding it so that the ant. sup. iliac spines and top of the symphysis pubis are in the same vertical plane |
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|
Term
|
Definition
- deeper with smaller aperatures
- more massiv ewith marked muscular impressions
- sciatic notches are deep and narrow
- superior aperture is heart-shaped and the acetabula face laterally
- the obturator foramina are round rather than oval |
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|
Term
|
Definition
- adapted for childbearing
- wider, shallower and has larger sup. and inf. apertures
- hip bones and ischial tuberosities are suaully farther apart because of broader sacrum adn wider pubic arch
- sacrum is flatter (less curved) whihc increases diameter of the birth canal and the ischial spines project less into the pelvic cavity
- subpubic angle is wide (90 degrees) |
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|
Term
|
Definition
1. levator ani
2. coccygeus
(pelvic diaphragm) |
|
|
Term
|
Definition
- muscles of the lower limb which originate in the pelvis and form part of the pelvic wall
1. obturator internus
2. piriformis
3. iliacus |
|
|
Term
|
Definition
- floor
- is composed of the levatir ani and coccygeus muscles together with the fasciae covering their superior and inf. surfaces
- it stretches across the floor of the pelvic cavity like a hammock and supports the abdominal and pelvic viscera
- pierced by anal canal, urethra, and vagina and is reinforced in the perineum by muscles an fasciae of the urogenital diaphragm |
|
|
Term
|
Definition
- broad, thin muscle forming most of the hammock-like floor of the pelvis
- The muscles of the two sides are separated from each other ventrally and are inserted into a raphe posteriorly.
- They function as a single unit across the midline
- The levator ani arises from the body of the pubis, the spine of the ischium and the arcus tendineus
- Muscle fibers from both sides are inserted into the coccyx and anococcygeal (median) raphe
- The entire levator ani is innervated by twigs from S2, S3, and S4 (and S5), as well as from the inferior rectal branch |
|
|
Term
|
Definition
| - tendinous arch; a thickened band of obturator internus fascia between the above two bony landmarks |
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|
Term
| Anoccocygeal (median) raohe |
|
Definition
| - narrow fibrous band extending from the coccyx to the post. margin of the anus |
|
|
Term
|
Definition
- part of the levator ani muscle
- arises from the dorsal surface of the pubis (and often the anterior tendinous arch) and is the more medial portion of the levator ani.
- An interval between the muscles from each side allows passage of the urethra, rectum and vagina.
- Parts of these muscles are close to the prostate in the male and the vagina in the female.
- Their fibers insert into the perineal body.
- Some fibers pass behind the rectum to join fibers from the other side to form the puborectalis muscle or "puborectal sling". |
|
|
Term
|
Definition
- part of the levator ani muscle
- arises from the arcus tendineus and spine of the ischium and inserts into the coccyx and anococcygeal raphe |
|
|
Term
|
Definition
- or ischiococcygeus
- the other muscle of the pelvic diaphragm
- situated post. to levator ani
- arise from spine of ischium and sacrospinous ligament and inserts into the coccyx and sacrum
- it assists the levator ani and has a similar innervation |
|
|
Term
| Supraanal fascia and infraanal fascia |
|
Definition
- or sup. and inf. fascia of pelvic diaphragm
- deep (investing) fascoas which are on either side of the pelvic diaphragm |
|
|
Term
|
Definition
- arises from sacrum and leaves pelvis through greater sciatic foramen
- laterally rotates hip
- not a true pelvic muscle |
|
|
Term
| Obturator internus muscle |
|
Definition
- occupies lateral wall of the internal surface of the lesser pelvis
- it arises from the sup and inf. pubic rami and from the obturator membrane
- passes through sciatic foramen to insert on the femur
- lateral hip rotator |
|
|
Term
|
Definition
- in abdominopelvic cavity separates organs from the body wall muscles
- divisible into 2 layers: transversalis fascia and subserous fascia |
|
|
Term
|
Definition
| - sheet of deep fascia on internal aspect of muscles surrounding the abdominopelvic cavity (ex: transversalis fascia on obturator internus muscle = obturator internus fascia) |
|
|
Term
|
Definition
- extraperitoneal, preperitoneal or subperitoneal fascia
- mostly fat, but it may also contain fibrous or even smooth muscle components
- located between peritoneum and transversalis fascia
- plays major role in support of pelvic organs
- condensations fo subserous fascia in various places have different names and are called ligaments |
|
|
Term
| pubovesical ligament (female) and puboprostatic ligament (male) |
|
Definition
| - anchor nexk of the bladder to pubis |
|
|
Term
| rectovesical ligament and rectovaginal ligament |
|
Definition
| connect the rectuma nd the bladder or vagina |
|
|
Term
| Cardinal (trasverse cervical or Machenrodt's) ligaments |
|
Definition
| - extend laterally from the cervix and upper vagina to deep fascia on the pelvic wall |
|
|
Term
| Uterosacral (sacrouterine)ligaments |
|
Definition
| - extend from the cervix to deep fascia on the sacrum |
|
|
Term
| Internal iliac (hypogastric) artery |
|
Definition
- begins at bifurcation of the common iliac artery ant. to the sacroiliac joint and follows a short, curved course toward the greater sciatic foramen
- one of the most variable arteries in the body
- supplies the walls of the pelvis, pelvic viscera, gluteal region, genital organs and part of the medial thigh
- usually divides into ant. and post. divisions and has 11 branches |
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|
Term
|
Definition
- branch of internal iliac artery
- ascends post. to the obturator nerve and the external iliac vessels to the medial border of the psoas major
- it divides into a lumbbar and an iliac branch to supply the psoas and iliacus muscles respectively |
|
|
Term
|
Definition
- branch of internal iliac artery
- give sup. and inf. branches to the ant. sacral foramina, vertebral canal and to the skin an dmuscles on the dorsal surface of the sacrum |
|
|
Term
|
Definition
- branch of internal iliac artery
- is the largest branch of the internal iliac. It usually passes between the lumbosacral trunk and the first sacral nerve to leave the pelvis through the greater sciatic foramen above the piriformis. |
|
|
Term
|
Definition
- branch of internal iliac artery
- usually passes between the 2nd and 3rd sacral nerves to descend between the piriformis and coccygeus muscles through the lower part of the greater sciatic foramen. |
|
|
Term
|
Definition
- branch of internal iliac artery
- may arise in common with the inferior vesical artery. It is distributed to the rectum, anal canal and prostate. It anastomoses with the superior rectal artery, a continuation of the inferior mesenteric artery and the inferior rectal artery, a branch of the internal pudendal artery. |
|
|
Term
|
Definition
- branch of internal iliac artery
- arises from the medial surface of the internal iliac and supplies the uterus. It passes superior to (over) the ureter at the level of the cervix and is located in the cardinal ligament of the uterus. |
|
|
Term
|
Definition
- usually arises from uterine artery (off internal iliac) but sometimes comes directly from internal iliac
- The uterine, vaginal and ovarian arteries anastomose with each other, with branches of the internal pudendal artery and with equivalent arteries on the other side. |
|
|
Term
|
Definition
- branch off internal iliac
- runs on the lateral wall of the pelvis to the obturator canal.
- In about 25% of the population, the obturator artery arises from the inferior epigastric or external iliac artery. When this occurs, it is called aberrant (anomalous) if it is the only obturator artery present. It is called accessory if it arises from the inferior epigastric artery when the normal obturator artery is present. |
|
|
Term
|
Definition
- branch of internal iliac
- distributed to the bladder, ureter, prostate and seminal vesical, and gives off the artery to the vas deferens (deferent artery) in the male.
- In the female, it is distributed to the bladder and ureter. |
|
|
Term
|
Definition
- branch of internal iliac artery
- is distributed to the superior portion of the bladder. There may be more than one of these. |
|
|
Term
| Obliterated umbilical artery |
|
Definition
- branch of internal iliac artery
- in the adult is a fibrous cord which is the remains of the fetal umbilical artery. It lies within the medial umbilical fold of peritoneum. |
|
|
Term
|
Definition
- branch of internal iliac artery
- leaves the pelvis through the greater sciatic foramen, enters the gluteal region, then passes through the lesser sciatic foramen to enter the perineum. It will be discussed again with the perineal region. |
|
|
Term
| lymphatic drainage of abdomen, pelvis, perineum, and lower extremity |
|
Definition
- tends to follow blood vessels and ligaments and passes through small clusters of nodes located on viscera or at birfurcations of vessels before draining into group or larger nodes along major vessels
- ultimately the nodes drain into the cisterna chyli |
|
|
Term
|
Definition
- takes dranage from abdomen, pelvis, perineum, and lower extremity
- drained sup. via thoracic duct into the junction of the left internal jugular vein and subclavian vein
- located on the bodies of L1 and L2 between the aorta and right diaphragmatic crus
- main tributaries are: lumbar trunks and intestinal trunk |
|
|
Term
|
Definition
- two
- drain lymph from paraaortic nodes
- lie at sides of the abdominal aorta
- lymph arises from:
1. lower limb, abdominal and pelvic walls
2. pelvic viscera
3. kidneys and adrenals
4. gonads |
|
|
Term
|
Definition
- drains lymph from preaortic nodes
- lymph usually arises from most abdomnal organs supplied by celiac trunk, sup and inf mesenteric arteries
- preaortic nodes are located on ant. surface of the aorta and cluster at the origins of the above 3 vessels |
|
|
Term
| Common, external, and internal iliac nodes |
|
Definition
- surround vessels of the same names and receive afferents from their areas of distribution
- they drain inguinal nodes, pelvic viscera, deep pelvic and abdominal walls, deep gluteal region and deeper aspects of the perineum |
|
|
Term
| Superficial inguinal nodes |
|
Definition
- located in the superficial fascia of the groin and form a "T" shape.
- The upper horizontal group parallels the inguinal ligament.
- The vertical group lies next to the greater saphenous vein.
These nodes drain:
superficial gluteal region
superficial anterior abdominal wall below umbilicus
external genitalia and skin of perineum
uterine lymphatics which follow the round ligament of the uterus
superficial lower extremity which follow the path of great saphenous vein
- Lymph from these nodes travels to deep inguinal nodes, then external iliac nodes, common iliac and paraaortic nodes (ultimately to cisterna chyli). |
|
|
Term
|
Definition
- vary in number from one to three.
- They are located in the femoral canal medial to the femoral vein and receive deep lymphatic drainage from the lower extremity along the path of distribution of the femoral vein and its numerous tributaries.
- Lymph from these nodes also travels to external iliac nodes and on to cisterna chyli. |
|
|
Term
| Lymphatic drainage of rectum |
|
Definition
1. superior half: follows path of superior rectal vessels to preaortic nodes around the inferior mesenteric artery
2. Inferior half: follows middle rectal vesssels to internal iliac nodes |
|
|
Term
|
Definition
- inferior to pectinate line: lymphatic drainage follows the same patha s other structures in the perineum to the superficial inguinal nodes
- superior to pectinate line: drainage is to internal iliac nodes |
|
|
Term
|
Definition
| - for the most part follows gonadal vessels directly to paraaortic nodes |
|
|
Term
| Fundus of uterus lymph drainage |
|
Definition
| - follows the path of either ovarian vessel to paraaortic nodes or round ligament of the uterus to superficial inguinal nodes and external iliac. |
|
|
Term
| Body of uterus lymph drainage |
|
Definition
| - follows uterine artery or cardinal ligament through the broad ligament to internal and external iliac nodes on the lateral wall of the pelvis. |
|
|
Term
| Cervix of uterus lymph drainage |
|
Definition
| - follows uterine or vaginal arteries to internal iliac. It can also follow the cardinal ligament to external iliac or the uterosacral ligament to sacral nodes. |
|
|
Term
|
Definition
1. sup.: accompany uterine artery to internal iliac nodes
2. middle: lymphatics accompany vaginal artery to internal iliac nodes
3. vestibules: drains mainly to superficial inguinal nodes |
|
|
Term
| Prostate and seminal vesicle lymph drainage |
|
Definition
| - drains to internal iliac, external iliac, and sacral nodes on wall of the pelvis |
|
|
Term
|
Definition
| - goes to internal iliac, common iliac, then paraaortic nodes |
|
|
Term
|
Definition
- diamond shaped area between the superomedial aspects of thighs
- it extends from the pubic symphysis along the ischiopubic rami to the ischial tuberosities along the sacrotuberous ligaments to the coccyx and from the inf. surface of the pelvic diaphragm above to the skin below
- the perineum is divided into 2 triangles: anal and urogenital triangles
- contains the external genitalia, erectile tissues, and associated muscles and fascias in addition to the urogenital diaphragm
- note that many clinicians define the perineum as the external surface of the perineal body, lying between the vulva and the anus in the female and the scrotum and anus in the male. |
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Term
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Definition
- branch of the internal iliac artery that enters the gluteal region through the greater sciatic foramen
- it then enters the perineum after crossing posterior to the spine of the ischium through the lesser sciatic foramen
- it lies in the pudendal (Alcock's) canal, a fascial tunnel on the medial aspect of the obturator internus muscle
- has 6 branches |
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Term
| Branches of the internal pudendal artery |
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Definition
1. inferior rectal artery: supplies rectum, anal sphincter, and anus
2. transverse perineal artery
3. perineal artery: supplies structures in deep and superficial spaces. Gives off post. labial/scrotal branches.
4. Deep artery of clitoris/penis: to corpora cavernosa
5. artery to bulb and corpus spongiosum
6. dorsal artery of the clitoris/penis |
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Term
| External pudendal arteries |
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Definition
- branches of femoral artery
- also supply perineal region |
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Term
| Venous drainage of the perineum |
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Definition
- mostly follows internal pudendal artery
- one exception is the deep dorsal vein of the penis/clitoris which passes inf. to the pubic arch directly into the pelvis to empty into the prostatic venous pelxus (male) or vesicular plexus (female) |
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Term
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Definition
- S2, 3, 4
- 3 main branches
1. inferior rectal nerve: motor to external anal sphincters and sensory to skin around anus. It also supplies the levator ani, along with twigs from sacral ventral rami
2. Perineal nerve:
a. superficial sensory branches: to scrotum/labia majora (post. scrotal/laial nerves)
b. deep motor branches; to muscles in the superficial and deep spaces
3. Dorsal nerve of clitoris/penis: is sensory to skin on the penis or clitoris |
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Term
| Perineal branch of post. cutaneous nerve of the thigh |
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Definition
| - sensory to labia majora and scrotum laterally |
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Term
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Definition
- Li
- is sensory to the ant. labia majora or scrotum (anterior labial/scrotal nerves) |
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Term
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Definition
- L1, L2
- Genital branch: is motor to cremaster muscle and sensory to small part of the scrotum or labia and adjacent thight (femoral branch is sensory to skin superficial to the femoral triangle |
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Term
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Definition
| - determined solely by physical forces acting across glomerular capillary |
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Term
| GFR at filtration equilibrium |
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Definition
- highly blood flow dependent
- changes in capillary blood flow change the fraction of the total capillary length that filters
- filtration fraction remains constant (at about 20% - 20% of water in plasma is filtered)
- filtration equilibrium is im[ptant because it allows GFR to eb controlled simply by controlling glomerular capillary blood flow (easily accomplished by adjusting afferent and efferent arteriolar resistance |
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Term
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Definition
| - the fraction of renal plasma flow that is filtered |
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Term
| Factors increasing afferent resistances |
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Definition
* norepinephrine
- to a lesser extent: endothelin, Adenosine*, and angiotensin II |
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Term
| Factors increasing efferent resistance |
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Definition
**Angiotensin II
- to a lesser extent norepinephrine and endothelin |
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Term
| Factors tat decrease afferent resistance |
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Definition
- Atrial n atriuretic peptide
- NO
- prostaglandin E2 |
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Term
| Factor decreasing efferent resistance |
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Definition
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Term
| Afferent vasodilation and total resistance, glomerular pressure and GFR |
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Definition
TR: decrease
GP: increase
GFR: increase |
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Term
| Afferent vasoconstriction and total resistance, glomerular pressure and GFR |
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Definition
TR: increase
GP: decrease
GFR: decrease |
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Term
| Efferent vasodilation and total resistance, glomerular pressure and GFR |
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Definition
TR: decrease
GP: decrease
GFR: decrease |
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Term
| Efferent vasoconstriction and total resistance, glomerular pressure and GFR |
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Definition
TR: increase
GP: increase
GFR: increase |
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Term
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Definition
For a substance (X) that is freely filtered and neither secreted into nor reabsorbed from the tubules, its rate of filtration will equal its rate of exretion in the urine. Moreover, its rate of filtration will equal GFR x plasma concentration. Thus the following relationship holds:
GFR x plasma[X] = urine[X]x volume/time
or
GFR = urine [X]x volume/time)/plasma [X]
- GFR is usually in mL/min or L/day (less frequently) |
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Term
| Criteria for substance used to measure GFR |
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Definition
1. must be a metabolically inert substance
2.it must be small enough in size (and not bound to protein) to be freely filtered
3.it must neither be secreted nor reabsorbed by the renal tubules.
- ex: inulin (gold standard) and iothalamate (new) |
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Term
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Definition
- used to measure GFR
- end-product of purine metabolism and leaves body only via kidney
- freely filtered and not reabsorbed, but secreted to a small extent
- no infusion needed as in inulin |
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Term
| Creatine levels and GFR estimate without urine sample |
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Definition
| - in steady state GFR can be estimated from the serum concentration of creatine |
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Term
| Problems with GFR estimate from serum creatine levels |
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Definition
1.Creatinine production decreases as muscle mass declines
2.Creatinine production is lower in women than in men
3.Creatinine production decrease with age (as, alas, our muscle mass decreases)
4.Creatinine production declines as GFR falls
5.Creatinine secretion increases as GFR falls |
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Term
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Definition
- formula to get accurate GFR from serum creatine levels:
Estimated GFR (ml/min/1.73 m2) = 186 x [serum creatinine]^-1.154 x age^-0.203
x 0.74 if female x 1.21 if African-American |
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Term
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Definition
1. The surface area for filtration and the water permeability of the GBM (Kuf)
2. The net ultratfiltration force - transcapillary hydrostatic minus oncotic pressure gradients (deltaP - deltapi)
3. Under most conditions, GFR is highly dependent on blood flow rate. |
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Term
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Definition
- at the cranial end of the sausage shaped structures that arise next to the developing aorta.
- disappear very quickly
- non-functional |
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Term
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Definition
- after pronephros, the rest of the "sausages" that form along the aorta
- functions for a few weeks and then disappears
- drains by the mesonephrenic (Wolffian) duct
- both ducts attach to the back wall of the bladder |
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Term
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Definition
- becomes the definitive kidney
- drained by ureteric bud
- is in the region of the caudal end of the mesonephros where the uteric bud attaches |
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Term
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Definition
| - tubular outgrowth that extends from each of the mesonephric ducts (right and left) and heads towards and eventually connects to the caudal end of the right and left mesonephros |
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Term
| Contributions of the metanephros |
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Definition
1. glomerulus
2. proximal and distal convoluted tubules |
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Term
| Contributions of the uteric bud |
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Definition
| 1. kidney drainage system (collecting ducts, calyceal system and the ureter) |
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Term
| Formation of separate holes for the ueter and vasa deferentia |
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Definition
| - the metnephric duct incorporates into the post. wall of the bladder resulting in the ureters having separate orifices into the bladder than the vasa deferentia |
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Term
| Placenta and kidney function |
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Definition
- performs kidney function during fetal life (excretion of nitrogenous waste)
- fetuses with bilateral renal agenesis can develop throughout gestation |
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Term
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Definition
- occurs in 0.25% of the pop.
- right and left metanephros come so close together that they fuse
- the arterial and mesonephric duct connections are established so the kidney otherwise develops normally
- when the normal ascent of the kidney ensues the fused caudal ends become "hung up" on the first caudal mid-line vessel they encounter (inferior mesenteric artery) |
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Term
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Definition
- absence of a kidney due to failure of connection of the metanephros and the uteric bud
- bilateral renal agenesis occurs in about 1 in 10,000 births |
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Term
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Definition
| - volume of plasma cleared of any substance of interest (including water itself) per unit time, usually in mL/min |
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Term
| Fractional excretion of X` |
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Definition
Cx/Ccreatine
- FEx
- fraction indicates the part of X arriving at the glomerular capillary per unit time that is excreted in the urine
(0.2 indicates 20% is excreted and thus 80% is reabsorbed) |
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Term
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Definition
- renal excretion of Na+ can vary
- in ECF expansion it increases to as much as 0.04 or 4%
- when tubule damage occurs in some renal diseases it also increase |
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Term
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Definition
- patients with major reduction in GFR
- have an FEk higher than 1.0 indicating that K+ must also be excreted by the tubules
- FEk+ is net result of the resorption and secretion |
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Term
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Definition
- PAH
-organic compound that at low levels is rapidly secreted by renal tubules
- 90% excretion
- as concentration increases, secretion sites are saturated and clearance drops, eventually approaching Cinulin (GFR)
- can calculate renal plasma flow (CPAH/0.9) only used for research (to calculate filtration fraction GFR/RPF) |
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