Components of the Digestive System

-Alimentary canal/ GI tract/ Digestive tract:

-Accessory organs:

Functions of the digestive system:

List the 8 major functions and what happens

PROTECTION

1. Ingestion: the taking of food into the mouth

2. Mastication: chewing movements of the materials and mixing it with saliva

3. Propulsion: movement of materials forward w/in GI tract (deglutition (swallowing), peristalsis, mass movements)

4. Mixing: moving back and forth to combine w/ digestive enzymes and break into smaller pieces

5. Secretion: added to lubricate, liquefy, and buffer materials to move through GI tract

6. Digestion: Chemical breakdown using enzymes

7. Absorption: Passage of molecules of food through mucous membrane of small intestines and into blood and lymph for distribution

8. Elimination: discharge of indigestible wastes

PROTECTION: From mechanical stresses, bacteria, chemical corrosion by acids and enzymes

How many layers does the GI tract have?

Name them

4 layers

1. Mucosa: innermost layer- simple columnar epithium. 

2. Submucosa

3. Smooth Muscle Layer

4. Serosa or Adventitia: outermost layer

Where is stratified squamous epithilum located?

What are its functions?

LOCATIONS: lining of mouth,

throat, esophagus, rectum, anus

FUNCTIONS: Provides physical

protection against abrasion,

pathogens, and chemical attack

-What are the most important glands of the stomach? 

-What do glands of the small intestine do?

-What do glands of the large intestine do?

-Those that secrete hydrochloric acid and pepsin (digestive enzymes)

- They secrete digestive enzymes and mucus that lubricates chyme

- Secrete mucus only

Where is villi located?

What do they do?

- in the small intestine-they are finger like projections into the lumen of the gut

-They enormously increase absorptive surface of the small intestine. Within each villus there is a capillary bed and a lymphatic lacteal (absorbs and circulates dietary lipids)

Where is simple columnar epithelium located?

What are its functions?

LOCATIONS: Lining of

stomach, intestine, gallbladder

FUNCTIONS:

Protection, secretion, absorption

-What does the submucosal layer contain?

-What does the submucosal layer act like? 

-Where is the myenteric plexus located?

- Contains postganglionic sympathetic nerve fibers and postganglionic parasympathetic nerve cells/fibers

- Acts as padding between layers and folds with mucosa when smooth muscle of the gut contracts

- In smooth muscle, in between the postganglionic sympathetic nerve fibers and postganglionic parasympathetic nerve cells/fibers

(outermost layer of GI tract)

Serosa (or viscerl peritoneum) exists only inferior to lower esophagus (below diaphragm) in the stomach, most of the small intestine and large intestine (areas adjeacent to the peritoneal cavity)

Adventitia is mostly connective tissue from surrounding tissues and found only on areas that are not adjacent to the peritoneal cavity ( esophagus and retroperitoneal cavity: some of the small+large intestines, pancreas)

What is Mesentary?

What is the mesocolon?

Double-layered peritoneal fold that supports the GI tract, gives the small intestine freedom for peristaltic movement. Provides a structure for the passage of intestinal nerves and vessels. 

Mesocolon is a specific portion of the mesentary that supports the large intestine

-Where does most of the lower digestive tract exist?

-Where does smooth muscle have the greatest accumulation?

- the peritoneal cavity

- in the walls of the digestive tract

-The GI tract is innervated by the _________ and _______ divisions of the ANS

What nerves are the source of the parasympathetic activity of the esophagus, stomach, pancreas, gallbladder, small intestine, and upper portion of the large intestine?

-The lower portion of the LI receives parasympathetic innervation from what nerves in the sacral plexus?

- sympathetic and parasympathetic

-Vagas nerves

-Spinal Nerves

• What sites innervate the smooth muscle of the GI tract?
• Are the effects of the sympathetic nerve stimulation to those of the parasympathetic nerve stimulation synergistic? 
• What does the ANS parasympathetic division produce in oral cavity?
• What does the sympathetic division produce?

• submucosal plexus and myenteric plexus 
• No, they are antagonistic
• thin, watery saliva
• think, mucous saliva

1. ingests food
2. receives saliva
3. grinds food and mixes with saliva (mastication)
4. initiates digestion of carbohydrates
5. forms and swallows soft mass of chewed food called bolus (deglutination) 

1-3. Describe the Pharynx

4. Name the Functions?

1. Mouth opens into oral/nasal pharynx narrowly w/ tonsils on lateral sides 
2. Where larynx seperates anteriorly: begins the respiratory path 
3. At this point, the pharynx narrows and becomes the esopgagus (running posteriorly)
4. Receive bolus and autonomically continues deglutination of bolus to esophagus

1. 1st stage is voluntary and follows mastication. The mouth is closed and breathing is temporarily interrupted. The bolus is formed
2. 2nd stage is the passage of the bolus through the pharynx. This stage is involuntary
3. 3rd stage is the entry and passage of the bolus of food through the esophagus. This stage is also involuntary.

-Esophagus description

-Function?

-Inferior to the pharynx

-travels through neck and upper part of the thorax behind trachea

-After trachea splits, the esophagus continues between lungs and behind heart, leaves the thorax piercing through the diaphragm, and ends at stomach

-Transports bolus to the stomach by peristalsis; lower esophageal sphincter restricts the backflow of food

1. Cardia- narrow upper region immeditely below the lower esophageal sphincter
2. Fundus- dome shaped portion of the left of and in direct contact with the diaphragm
3. Body-large central portion
4. Pylorus- funnel shapped terminal portion. It regulates the movement of chyme into the SI prohibiting the backflow-pyloric sphincter is the modified circular muscle at the end of the pylorus where it joins the SI

Where is the Greater Omentum?

Where is the lesser omentum?

What do these structures do?

1. Extends from the greater curvature of the stomach to the travsverse colon, forming an apron-like structure over most of the small intestine.
2. Passes from the lesser curvature of the stomach and the upper duodenum to the inferior surface of the liver.
3. Functions include: storing fat, cushioning visceral organs, supporting lymph nodes, and protecting against the spread of infection

-How many muscular layers does the stomach have? Name them.

- What is rugae?

-Name the 4 main cells that line the epithelial cells of stomach and what they secrete

-3: outer longitudinal, middle circular and inner oblique

-Rugae are specialized folds in the two innermost layers of the stomach that allows for the distention of the stomach without injuries as it fills with material

-1.Surface mucous cells and mucous neck cells

Enterchromaffin Cells: secrete histamine

Somatostatin Containing Cells: secrete somatostatin

Gastrincontaining cells: secrete the hormone gastrin

1. Receives bolus from the esophagus 
2. Churns bolus with gastric juice
3. Initiates digestion of proteins 
4. Carries out limited absorption
5. Moves mixture of partly digested food and secretions (chyme) into the duodenum and prohibits the backflow of chyme 
6. Regurgitates when necessary
7. Generates hunger pains which causes disire to eat 

-Is the regulation of gastric secretions strictly neural?

-Neural mechanisms in the brain originate in the _____ and through local reflexes in the ______ _____ system

-Describe the 3 phases of gastric regulation

- No, it is neural and hormonally controlled mechanisms 

- Medulla, Enteric Nervous System 

1. Cephalic: 1st phase- see an increase in stomach secretions, see the anticipation of food
2. Gastric: 2nd phase- the most stimulating phase of secretion, see the greatest volume of secretions produced
3. Intestinal: Final phase- see a decrease in secretions as chyme from stomach passes into the SI 

Small Intestine

-Name parts and describe

1. Deodenum- receives bile from the liver and gallbladder, and pancreatic juices
2. Jejunum- absorption occurs primarily here (some in other parts too)
3. Ileum- lymph nodes, called mesenteric plexus, are abundant in the walls

Small Intestine 

-Functions

1. Receives chyme from the stomach and secretions from the liver and pancreas 
2. Chemically and mechanically breaks down chyme
3. Absorbs nutrients
4. Transports wastes through peristalsis to large intestine
5. Prohibits the backflow of intestinal waves from the large intestine 

1. What is the largest internal organ of the body?

1. Liver

1. Names the 4 lobes of the liver
2. What is the ligament that seperates the left from the right lobe?
3. The outer capsule of the liver invaginates internally to seperate out the liver into _____ lobules. Each contain a ________ at each corner and a central vein in the center.
4. What is bile and where is it made?
5. What is between each hepatic cord?

1. Right, left, caudate, and quadrate lobes
2. Falciform ligament
3. hexagonal, portal tirad (portal vein, hepatic artery, hepatic duct).
4.  Bile- a liver secretion that is stored and concentrated in the gallbladder and released into the deodenum; essential for the absorption of fats. Comes from hepatocytes, arranged into hepatic cords coming from the central vein of the liver. 
5. A bile canalicili, from which the bile produced in the hepatocytes drains into

- A serous membrane reinforced with connective tissue that attaches the liver to the diaphragm and anterior abdominal wall 

-The falciform is the remnant of the fetal umbilical vein

-What is the Gallbladder?

-What does the Gallbladder do?

- Saclike organ that is attached to the inferior surface of the liver

-It serves to store and concentrate bile

-Autonomic innervation is the same as that of the liver

Pancreas

• What's it do?

• Is it an exocrine or an endocrine functioning organ?

• A mixed gland because it produces both endocrine and exocrine functions 
• Both

-Endocrine functions- cells called the pancreatic islets secrete the hormones insulin and glucagon into the blood

Exocrine functions- secretes pancreatic juice that enters the duodenum