Term
| 5 main areas that secrete H2O, digestive juices & enzymes |
|
Definition
mouth (salivary glands)
stomach (gastric glands)
pancreas
liver (gallbladder)
small intestine |
|
|
Term
What gland secretes each?
1. Serous, watery secretion
2. produce a mixed serous/mucus secretion
3. predominantly mucus secretion |
|
Definition
parotid
submandibular
sublingual |
|
|
Term
| What are the secretory units ofo the salivary glands |
|
Definition
|
|
Term
| ___ controls the viscosity of mucus |
|
Definition
|
|
Term
3 functions of saliva
1. Initial digestion of ___ by the salivary enzyme ___. Breaks down polysaccharides into disaccharides (maltose)
2. ___ & ___ of ingested foods
3. ___ of ingested food to aid its movement |
|
Definition
starches by a-amylase
dilution and buffering
lubrication |
|
|
Term
| Starch and glycogen are polysaccharides that fxn to ___. |
|
Definition
|
|
Term
| how much saliva is produced/day? |
|
Definition
|
|
Term
|
Definition
water
mucin - glycoprotein, mucus-rich secretion
protein: amylase enzymes
salts: Na, Cl, K, HCO3 |
|
|
Term
Two secretory cells composed of acinus in salivary glands
1. ___: secrete water fluid containing digestive enzymes like amylase
2. ___: secrete mucin |
|
Definition
|
|
Term
| Amylase is synthesized and stored in the ___ granules |
|
Definition
|
|
Term
| The ___ modifies electrolye concentrations of the saliva. |
|
Definition
|
|
Term
Primary secretion of saliva produced by acinar cells is __tonic, with salt concentrations that are close to that of the plasma.
The ductal cells modify the composition of the saliva, causing __tonic character, at the low flow rate of 1ml/min.
To do this, the ductal cells extract __ and __, making their concentrations less than that in the plasma, and they add __ & __, resulting in concentrations greater than that in the plasma. |
|
Definition
isotonic
hypotonic
Na, Cl
K, HCO3 |
|
|
Term
Relationship between saliva and salivary flow rate:
The less difference in ion concentration between saliva and plasma, the more/less modification is done by the ductal cells.
The higher the flow rate, the less time there is for modification by ductal cells.
Therefore, ionic concentraiton is __-dependent |
|
Definition
|
|
Term
| What is a high or low salivary flow rate? |
|
Definition
high = >1 ml/min
low = < 1 ml/min |
|
|
Term
REgulation of salivary secretion:
1. Both parasympathetic and sympathetic stimulation of salivary glands increases/decreases activity of acinar and ductal cells, thereby increasing/decreasing salivary secretion
- the ___ system predominantly controls salivary secretion
___ is an anti-cholinergic acent (Ach-M receptor antagonist) and is a protein inhibitor of salivary secretion.
2. ___ causes reflex secretion of saliva. |
|
Definition
increase, increase
parasympathetic
atropine
food in the mouth |
|
|
Term
Relatively common, chronic, autoimmune systemic inflammatory disorder of unknown cuase
characterized by dryness of the mouth, eyes, and other mucus membranes due to ___ of the exocrine galnds and secondary gland dysfunction.
Pathophysiology:
Salivary lacrimal, and other exocrine glands become infiltrated with CD4 cells and with B cells, resulting in ____.
Symptoms:
Diminished saliva (xerostomia) results in difficulty chewing, swallowing, candida infection, tooth decay, calculi in salivary ducts. possible diminished taste and smell. |
|
Definition
sjogren's syndrome
lymphocytic infiltration
ductal luminal narrowing and atrophy of glands |
|
|
Term
Storage capacity of the stomach?
How much gastric juice does it secrete per day? |
|
Definition
4 cups
2000-2500 ml (2- 2.5L) |
|
|
Term
Functions of the stomach:
Serves as a ___, mixes and subdivides food
Secretes 5 things
Digests ___
Empties food at a controlled rate into the duodenum |
|
Definition
reservoir
HCL, pepsinogens, mucus, HCO3, intrinsic factor
--> HCL kills micro-organisms
proteins |
|
|
Term
| ___ is the pre-proenzyme precursor of pepsin |
|
Definition
|
|
Term
What is the optimal pH of the stomach?
What happens if the pH is above this? |
|
Definition
1-4
higher pH = significant |
|
|
Term
| What is a possible outcome of achlorhydria, gastrectomy, or GI disease? |
|
Definition
| increased risk of bacterial overgrowth in the intestines due to decreased acid |
|
|
Term
| Protein digestion begins with ___ which is converted to active pepsin in acidic stomach environment. |
|
Definition
|
|
Term
Gastric mucosa has numerus openings called ___.
__ secrete a fluid called gastric juice.
4 major components of gastric juice? |
|
Definition
gastric pits
gastric (oxyntic) glands
acid (HCl)
enzymes (gastric lipase)
mucus (protects stomach and forms chyme)
hormones (gastrin, intrinsic factor) |
|
|
Term
4 types of secretory epithelial cells that cover the surface of the stomach and extend down into gastric pits and glands:
1. __: secrete alkaline mucus that protects the epithelium against shear stress and acid.
2. __: secrete HCl
3. __: secrete pepsinogen
4. __: secrete gastrin |
|
Definition
mucus
parietal
chief
g cell |
|
|
Term
Mechanism of HCl secretion by gastric parietal cells:
1. Within parietal cells CO2 produced from aerobic metabolism combines with H2O to form H2CO3. This reaction is catalyzed by ___. H2CO3 then dissociates into H+ and HCO3.
2. At the apical membrane, H+ is secreted into the lumen of the stomach via the ___. Cl follows H+ into the lumen by diffusing through ___ in the apical membrane.
3. At the basolateral membrane, HCO2 is absorbed into the blood via a ___ exchanger. The absorbed HCO3 is responsible for the ____ (high pH) that can be observed in gastric venous blood after a meal. Eventually this HCO3 will be secreted back into the GI tract in pancreatic secretions |
|
Definition
1. carbonic anhydrase
2. H+ K+ ATPase, Cl- channels
3. Cl-HCO3 , alkaline tide |
|
|
Term
| H+-K+ ATPase in step 2 of HCl secretion by gastric parietal cells is inhibited by the drug ___, which is used to treat ulcers to reduce H+ secretion. |
|
Definition
|
|
Term
| Net results from gastric parietal cell events are? |
|
Definition
net secretion of HCl
Net absorption of HCO3- |
|
|
Term
Regulation of HCl secretion:
ACh:
release by __ nerve
binds to receptors on __ cells
produces H+ secretion by ___ cells
___ blocks the action of ACh by blocking muscarinic receptors on these cells |
|
Definition
vagus
parietal
parietal
atropine |
|
|
Term
Regulation of HCl secretion:
Histamine:
Released from ___ cells in gastric mucosa
Binds to __ receptors on parietal cells
stimuates parietal cells to secrete __
__ blocks these receptors |
|
Definition
mastlike cells
H2
H+
cimetidine |
|
|
Term
Regulation of HCl secretion:
Gastrin:
Released into circulation by __ cells of the stomach antrum
Binds to receptors on __ cells
Stimulates __ secretion |
|
Definition
|
|
Term
___ is a glycoprotein produced by the parietal cells
It is necessary for the absorption of B12, which takes place in the terminal ileum
Lack of this substance is seen in ____, an autoimmune disease. Deficiency can also lead to malabsorption of B12 and subsequent ___. |
|
Definition
intrinsic factor
pernicious anemia
megaloblastic anemia |
|
|
Term
| Lack of intrinsic factor or B12 deficiency or something can result in CNS disease via damage to the ___, resulting in problems with balance and 2 point discrimination |
|
Definition
|
|
Term
The gastric mucosal barreir in physiological conditions:
The innermost layer of gastric mucosa (epithelia) is impermeable to the acid it secretes. the protective effects are attributed to the following factors:
___ - prevent acid penetration
The epithelia are covered with the _____, which is an impermeable hydrophobic lipid layer to prevent from ionized water-soluble molecules |
|
Definition
tight junctions
gastric mucosal barrier |
|
|
Term
Pathophysiology of peptic ulcer:
Gastric secretions induce ___ damage.
Occur in what three places? |
|
Definition
mucosal barrier
first few cm of duodenum (most common), antrum of stomach, lower esophagus
|
|
|
Term
Causes of peptic ulcer:
1. Disruption of mucosal barrier:
- ___ cuases 75-95% of all ulcers
- risk factors?
- ischemia
2. Excess H+ and pepsin
- ___ disease: rare gastrinoma, gastrin-producing tumor
- psychic stress-increased parasympathetic stimulation |
|
Definition
H. pylori
smoking, alcohol, NSAID, stress, reflux or bile salts, proteases, free radicals
zollinger-ellison |
|
|
Term
Gastric ulcers:
Mucosal barrier is defective allowing H+ and pepsin to digest part of the mucosa
H. pylori produces __ from urea, which breaks down mucosal barrier |
|
Definition
|
|
Term
Duodenal ulcers:
__ secretory rates are higher than normal
- Excess damage to mucosa, often confused wtih pain of being hungry |
|
Definition
|
|
Term
What diesase?
Prevalence of middle aged adults is 20-50% in industrialized countries.
Transmission via vomit, saliva, feces, H2O
Inflammation occurs in antrum and body of stomach, leading to gastric atrophy and peptic ulcer |
|
Definition
|
|
Term
What disease?
Rare condition caused by a gastrinoma. the tumors most likely exist in the pancreas but can also be found in stomach or duodenum.
Elevation of serum gastrin level and basal gastric acid in staomch
peptic ulcer |
|
Definition
| Zollinger-Ellison Syndrome |
|
|
Term
|
Definition
Primary: serve as portal whereby nutrients and water can be absorbed into the body
- mix food with a variety of secretions from the GI tract and digestive secretions
- move food along the GI tract
- Absorb nutrients to supply metabolic needs
- Excrete waste |
|
|
Term
|
Definition
mouth
salivary glands
pharynx
esophagus
stomach
exocrine pancreas
liver
small intestine
large intestine |
|
|
Term
| What do the bacteria in the GI tract accomplish? |
|
Definition
metabolic fxns that can't be performed by mamallian enzymes
resistance to infection |
|
|
Term
| Components of the immune system of the GI tract |
|
Definition
Enteric immune system (little brain): myenteric and submucosal plexi
splanchnic circulation
Neuroendocrine system including VIP |
|
|
Term
| 4 basic digestive processes |
|
Definition
motility
secretion
digestion
absorption |
|
|
Term
| 4 layers of the GI tract wall |
|
Definition
mucosa (mucus membrane, lamina propria, and
muscularis mucosa)
submucosa
muscularis externa (outer longitudinal and inner circular muscles)
serosa
listed in to out |
|
|
Term
GI tract layers: Mucosa
Components?
Functions? |
|
Definition
COmponents: Epithelium
lamina propria (loose connective tissue contains lymph nodes and capillaries)
muscularis mucosa (smooth muscle that contracts to change shape and surface areas)
Functions:
Produce mucus
secrete enzymes
absorb nutrient
protect pathogens from entry - first line of defense of the immune system |
|
|
Term
GI tract layers: Submucosa
components? |
|
Definition
connective tissue
blood vessels
glands
submucosal nerve plexus (meissner's plexus) |
|
|
Term
GI tract layers: muscularis
2 layers?
nerve plexus? |
|
Definition
inner circular layer
outer longitudinal layer
myenteric nerve plexus (auerbach's plexus) - located between the layers |
|
|
Term
GI tract layers: serosa
components? |
|
Definition
single layer of sqamous cells called mesothelium
small amount of connective tissue
|
|
|
Term
What is the function of the enteric nervous system?
what are the targets? |
|
Definition
function: itegrate motor and secretory activity of GI tract
Targets; smooth muscle and glands |
|
|
Term
| 2 nervous system controls of digestion - intrinsic and extrinsic |
|
Definition
Intrinsic: enteric nervous system
- myenteric plexus, submucosal plexus
extrinsic: autonomic nervous system |
|
|
Term
| The autonomic ns influences motor and secretory activities through the ____ |
|
Definition
|
|
Term
|
Definition
|
|
Term
| Can enteric NS work in absence of ANS? |
|
Definition
|
|
Term
| 4 types of neurons of the ENS |
|
Definition
motor - innervate smooth muscle
secretory - regulate endocrine and exocrine secretion
sensory - detect stretch, tonicity, glucose, or amino acids
interneurons - interact among neurons |
|
|
Term
| Where do the different parts of the ENS (myenteric and submucosa plexuses) exist? |
|
Definition
myenteric - everywhere
submucosa - mainly in intestines. sparse in stomach. not in esophagus |
|
|
Term
HIstamine is an example of a ___ substance
Insuline is an example of a ___ substance |
|
Definition
paracrine
endocrine (hormoen) |
|
|
Term
What substance?
contraction of SMC in wall
relaxation of spincters
stimulation of secretions |
|
Definition
|
|
Term
What substance?
relaxation of smc in wall
contraction of sphincters
inhibition of salivary secretion |
|
Definition
norepinephrine
(adrenergic) |
|
|
Term
What substance?
relaxation of SMC
stimulation of secretions |
|
Definition
|
|
Term
| Which substance causes stimulation of gastrin secretion? |
|
Definition
| gastrin-releasing peptide |
|
|
Term
Which substance?
contraction of smooth muscle
stimulation of salivary secretion |
|
Definition
| substance P (cosecreted with ACh) |
|
|
Term
2 types of neurons in the ENS
1. ___: multiple axons, long-lasting hyperpolarization, interneurons, largest proportion in myenteric plexus
2. ___: single long axon, no hyperpolarization, most of submucosal plexus |
|
Definition
after-hyperpolarization neurons (AH-type)
synaptic neurons (S-type) |
|
|
Term
| What substance bocks S-type neurons? |
|
Definition
|
|
Term
Similarities between sympathetic and parasympathetic NS:
1. Both are __ (motor) systems
2. Both involve regulation of the ___ environment, out of our conscious control.
3. Both involve 2 neurons that synapse in a ___
4. Both innervate __ & ___ |
|
Definition
efferent (visceromotor)
internal
peripheral ganglion
glands & smooth muscle |
|
|
Term
Differences between sympathetic and parasympathetic:
Lengths of neurons.
____ has a short preganglionic neuron and a long postganglionic neuron
___ has a long preganglionic neuron and a short postganglionic neuron |
|
Definition
sympathetic
parasympathetic |
|
|
Term
The ____ NS consists of craniosacral nerves: Vagus, plus S2-S4.
The ___ consists of thoracolumbar nerves: T1-L2/3 |
|
Definition
parasympathetic
sympathetic |
|
|
Term
| 3 prevertebral sympathetic ganglia |
|
Definition
celiac
superior mesenteric
inferior mesenteric |
|
|
Term
Acetylcholine is involved in the sympathetic/parasympathetic ns
NE is involved in the sympathetic/parasympathetic NS |
|
Definition
|
|
Term
| Symptoms associated wtih motility disorders |
|
Definition
heartburn
nausea
vomiting
stomach pain
constipation
diarrhea |
|
|
Term
| The electrical output of GI muscles is a product of contributions from two electrically coupled cell types: |
|
Definition
Smooth mucle cells
interstitial cells of Cajal (ICC) |
|
|
Term
What type of cell?
- type of interstitial, modified smooth muscle cell
- is the pacemaker cell of the GI tract (generates AP)
- forms a network among one another
- is responsible for slow wave GI tract smooth muscle AP |
|
Definition
| interstitial cell of cajar (ICC) |
|
|
Term
What type of cell?
- respond to the depolarization/repolarization (ap) cycle imposed by ICC
- are organized as a structural and functional unit (an electrical syncytium)
- are electrically conducted via low-resistance gap junctions between cells
- circular and longitudinal cell contraction result in decreased diamenter and shortening length the that segment of tube.. which moves food forward |
|
Definition
|
|
Term
Phases of AP of SMC
Phase 0
Phase 1
Phase 2
Phase 3
Phase 4 |
|
Definition
0: resting MP
1: upstroke: voltage gated Ca2+ channels and voltage gated K+ channels open
2: transient outward K+ current. early repolarization
3: inward Ca current and outward K current - plateau
4: inactivation of voltage-gated Ca channels and activation of Ca gated K channels |
|
|
Term
When membrane potential of a slow wave is lower than threshold, no AP is generated, but the muscle undergoes ___, characterized by small contraction and incomplete relaxation
When threshold is reached, an AP is generated and the the muscle undergoes ___.
What is the purpose of this process? |
|
Definition
tonic contraction
phasic contraction
makes sure contraction of some sort is always happening so peristalsis can continue |
|
|
Term
| ____ of muscles generated by slow wave are the basis for peristalsis and segmentation |
|
Definition
|
|
Term
4 patterns of GI motility
___: controlled movment of content in GI tract from stomach to large intestine
___: crushing and grinding of ingested food
___: segmentation
___: tonic movement. movements consist of a constant level of contraction or tone wtihout regular periods of relaxation. Found in lower esophagus and upper stomach and ileocecal valve and internal anal sphincter. |
|
Definition
propulsion
trituration
mixing movment
reservoir function |
|
|
Term
| Where does carbohydrate digestion begin? |
|
Definition
| mouth - when carbs mix with salivary amylase |
|
|
Term
3 phases of swallowing:
1. ___: (voluntary) in the mouth. the Bolus is collected at the back of the mouth so the tongue can lift the food upward and into the pharynx to stimulate the swallowing reflex
2. ___: (involuntary). upper esophageal sphincter relaxes. superior constrictor muscle contracts forcing food into esophagus.
3. ___: (involuntary). peristalsis moves food through the esophagus into the stomach |
|
Definition
oral phase
pharyngeal phase
Esophagus phase |
|
|
Term
| During the pharyngeal phase of swallowing, food movement into the respiratory passage is prevented by what? |
|
Definition
| the tongue elevates and presses against the soft palate, closing the epiglottis |
|
|
Term
|
Definition
Receptor near pharynx are activated.
afferent nerves (CN IX and X) are activated
Integrator/controller located in medulla
Efferent nerve
Contraction of pharyngeal skeletal muscle
Relaxation of upper esophageal sphincter |
|
|
Term
| Primary and secondary peristalsis |
|
Definition
Primary follows reflexes, is controlled by swallowing center in brainstem
secondary occurs when primary is inadequate to move food through esophagus (esophageal obstruction) |
|
|
Term
___: (heartburn) - common esophageal discomfort
is the result of regurgitation of food and gastric fluid into the lower esophagus |
|
Definition
|
|
Term
|
Definition
|
|
Term
| 3 layers of stomach muscle |
|
Definition
longitudinal
circular
oblique |
|
|
Term
|
Definition
| reservoir, mixing, subdividing, controlled emptying into duodenum |
|
|
Term
Reservoir fxn of stomach (receptive relaxation) is mediated by ___ & ___. How does it work?
2 stimuli? |
|
Definition
vagus and VIP (vasovagal reflex)
once food gets into the stomach, it stimulates stretch, osmotic, and chemical receptors to send signals to the medulla through afferent vagus nerves, which sends signal through the vagus motor nerve to tell stomach wall to distend
stimuli: stretch and CCK |
|
|
Term
___ - the semi-liquid food mixture in the stomach
___ - needed to digest fat and protein (not carbs) stimulate receptive relaxation |
|
Definition
|
|
Term
| ___ - phasic contraction that begins in the middle of the stomach. Necessary for mixing and trituration of the gastric contents. |
|
Definition
|
|
Term
| ___: the wave of contraction that closes the pylorus, resulting in most of the chyme propelled back, further mixing reduction of particular size |
|
Definition
|
|
Term
Emptying of chyme into the duodenum takes about __hr after a meal
The rate of emptying depends on what two factors? |
|
Definition
3 hr
on the time for neutralization of H+ (by pancreatic HCO3) and the content of the food (liquid food faster than solid) |
|
|
Term
Gastric emptying:
More H+ and CCK induced by fat in the duodenum = more/less time for emptying |
|
Definition
|
|
Term
Autonomic control of gastric motility:
___ enhances peristatltic contractions (rest and digest)
___ inhibits peristaltic contractions (fight or flight) |
|
Definition
parasympathetic
sympathetic |
|
|
Term
| Differences in motility in fed vs. fasting states |
|
Definition
fed - antrum contracts at a rate of 3/min
Fasting - antrum is quiescent for 1-2 hrs, then a 10-20 min period of intense contractions with a relaxed pyloric sphincter when indigestible objected remained from previous meal get emptied into stomach, followed by another quiescent period
|
|
|
Term
| The fasting motility pattern is called the ____ |
|
Definition
| migrating myoelectric complex (MMC) - contractions that occur every ~90 min and fxn to clear stoamch of residue remaining from previous meal |
|
|
Term
| Formation of duodenal v. gastric ulcers |
|
Definition
Duodenal - duodenum is basic, so when gastric emptying is too rapid, a duodenal ulcer develops due to excess acid
Gastric - the stomach is acidic, so when duodenal contents are regurgitated into the stomach, an ulcer develops due to excess base. Gastric ulcers may be exacerbated by slow gastric emptying |
|
|
Term
| 2 primary fxns of small intestine |
|
Definition
digestion
absoprtion of nutrients |
|
|
Term
frequency of small intestine peristalsis
contraction pattern?
how is it regulated? |
|
Definition
12/min (constant)
primary contraction - segmentation (mixing)
Secondary - peristalsis (moving fwd)
regulated by enteric reflex:
Activated by PSNS
inhibited by SNS |
|
|
Term
Fxns of large intestine
Mucosa contains tubular glands called ___ that are responsible for mucus secretion |
|
Definition
reabsorb water and electrolytes
eliminate waste
storage
crypts |
|
|
Term
Colon:
Segmental contractions of ___ facilitate H2O absoprtion
Mass movment is the forecful peristaltic contraction over long distances after a meal, called the ____. Happens 1-3 times/day. |
|
Definition
haustra
gastric-colic reflex |
|
|
Term
Anal reflexes:
Distention of the rectum results in ____
Reflex relaxation of ___ sphincter
Reflex constriction of ___ sphincter |
|
Definition
urge to defecate
internal anal
external anal |
|
|
Term
| Where is vomitting controlled? |
|
Definition
| vomiting center in medulla |
|
|
Term
Small intestine:
___: finger-like projections of the mucosa that contain capillaries
___: tiny projections on the luminal membrane of each cell that give the apical region a striated apearance called the ___. |
|
Definition
villi
microvilli
brush border |
|
|
Term
| ___ - a lymphatic capillary that absorbs ingested fat |
|
Definition
|
|
Term
GI Peptides:
Include what 3 things?
Regulate what 5 fxns of the digestive tract? |
|
Definition
hormones, neurocrines, paracrines
contraction and relaxation of smooth muscle wall and sphincters
secretion of enzymes for digestion
secretion of fluid and electrolytes
trophic (growth) effects
Some regulation secretion of other peptides |
|
|
Term
| What are some hormones that are released by the GI tract to act either on the GI tract or elsewhere in the body? |
|
Definition
Gastrin
CCK
secretin
GIP (gastric inhibitory peptide)
|
|
|
Term
___ are secreted by the endocrine cells of the GI tract and they act locally within the same tissue that secreted them.
An example is ___, which is inhibitory and is released from the small intestine |
|
Definition
|
|
Term
____ are peptides released by neurons of the GI tract following an AP
They include... (6)? |
|
Definition
neurocrines
ACh
NE
VIP
GRP
Neuropeptide Y
Substance P |
|
|
Term
Gastrin:
Secreted by __ cells in the stomach in response to eating
___ is released from vagal nerve endings onto these cells to stimulate gastrin release.
___ inhibits gastrin secretion
Gastrin promotes ___ secretion by gastric parietal cells
Gastrin promotes ___ also |
|
Definition
G cells
GRP (Gastrin releasing peptide)
low pH in stomach
H+
growth of gastric mucosa |
|
|
Term
CCK:
Secreted by __ cells of the small intestine in response to fatty acid and small peptides
5 actions? |
|
Definition
I cells
contraction of gallbladder to eject bile into small intestine to emulsify lipids
Secrete pancreatic enzymes to digest lipids, CHO, and proteins
Secretion of bicarbonate (HCO3) from pancreas
Growth of exocrine pancreas and gallbladder
Inhibition of gastric emptying (slows rate) to ensure adequate time for digestion |
|
|
Term
Secretin:
Secreted by __ cells of the duodenum in response to H+ and fatty acids
Promotes secretion of ____ from the pancreas to neutralize H+ and allow for pancreatic enzymes to digest fat
INhibits effects of __ on parietal cells by inhibiting H+ |
|
Definition
|
|
Term
Gastric INhibitory Peptide (GIP)
Secreted by the small intestine in response to ___, ___, and ___
Stimulates ___ secretion by the pancreas
Inhibits ___ secretion |
|
Definition
CHO, amino acis, fatty acids
insulin
gastric H+ |
|
|
Term
Somatostatin:
Secreted by __ cells in the gastric antrum in response to decreased luminal pH
Inhibits secretion of ____ & ____ |
|
Definition
D
other GI hormones and gastric acid |
|
|
Term
Histamine:
Secreted in ___ region of stomach
Stimulates __ secretion by gastric parietal cells (along with ___ & ___) |
|
Definition
H+-secreting region
H+, gastrin, ACh |
|
|
Term
The pancreas is an exocrine and endocrine gland.
Exocrine fxn done by ___ cells:
- secrete essential digestive enzymes through pancreatic duct into the duodenum
Endocrine fxn done by ___:
- secrete insulin and glucagon into the blood stream |
|
Definition
acinar cells
islets of langerhans |
|
|
Term
Exocrine pancreas:
- secretes _L/d into the duodenum
- Fluid consists of __ to neutralize H+ in the duodenum from the stomach and ___ which digest CHO, proteins, and lipids into absorbable molecules
Exocrine glands make up about __% of the pancreas
___ cells line the blind end of the branching duct system and secrete the enzymatic portion
___ cells line the ducts and secrete the aqueous HCO3 component |
|
Definition
1 L/d
HCO3-, enzymes
90%
Acinar cells
Ductal cells |
|
|
Term
| The optimal pH for pancreatic enzymes is ___ |
|
Definition
|
|
Term
HCO3- secretion by pancreatic ductal cells:
The ___ membrane of ductal cells contains a Cl-HCO exchanger
The ___ membrane contains a Na/K ATPase and a Na/H exchanger
How these work:
- CO2 and H2O combine to form H+ and HCO3-
- HCO3 is secreted into the pancreatic juice by the ___ (pump)
- H+ is transported into the blood by the ___ (pump), which causes acidification of pancreatic venous blood. |
|
Definition
apical
basolateral
Cl-HCO3 exchanger
Na/H exchanger |
|
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Term
Regulation of enzymatic pancreatic secretions by acinar cells
Receptors for:
1. ___: most important stimulant
2. ___: also stimulates enzyme secretion
By what mechanism do these substances stimulate enzymatic secretion? |
|
Definition
CCK
ACh
stimulate enzymatic secretion via IP3 and Ca2+ |
|
|
Term
Regulation of pancreatic aqueous secretion of HCO3 by Ductal cells:
Receptors for 3 things.
Which is most important stimulant?
By what mechanism does this substance stimulate HCO3 secretion? |
|
Definition
CCK, ACh, Secretin
Secretin is most important, but it's effects are potentiated by CCK and ACh
Secretin stimulates HCO3 secretion via cAMP |
|
|
Term
What nutrient do these enzymes digest?
Pancreatic: amylase
Intestinal: sucrase, maltase, lactase, trehalase, a-dextrinase, amino-oligopeptidase, dipeptidase, enterokinase |
|
Definition
|
|
Term
What nutrient do these pancreatic enzymes digest?
trypsin
chymotrypsin
carboxypeptidase
elastase |
|
Definition
|
|
Term
what nutrient do these pancreatic enzymes digest?
lipase-colipase
phospholipase
cholesterol ester hydrolase |
|
Definition
|
|
Term
Bile:
Necessary for the digestion and absorption of ___ in the small intestine.
Composed of ___, ___, and ___
Solubilize products of __ digestion into packets called ___. |
|
Definition
lipids
bile salts, bile pigments, cholesterol
lipid, micelles |
|
|
Term
Bile:
Produced and secreted by the ____
Stored in the ___
Injected into the ___
After lipids are absorbed, bile salts are recirculated to the liver via the ____, where they are extracted from portal blood by ___. |
|
Definition
liver
gallbladder
small intestine
enterohepatic circulation
hepatocytes |
|
|
Term
A female pt with crohn's disease undergoes an ileectomy. Afterwards, she notices oil droplets in her diarrhea. What is this condition called and what caused it?
What are other complications of this surgery?
What would treat the diarrhea? |
|
Definition
Steatorrhea
After the ileectomy, the intestine is unable to reabsorb the normal amount (95%) of bile salts. The liver cannot keep up with the increased need for making bile salts and thus lipids are not fully digested and end up in her stool as oil droplets
The diarrhea is caused bc the exces bile acids in the intestine stimulate Cl- secretion. Excess Cl stimulates excess Na and H2O to be secreted into the lumen, resulting in diarrhea.
Also the pt will not be able to absorb adequate intrinsic factor-B12 complex, bc this normally happens in the ileum... so the pt will need monthly B12 injections
Cholestryamine to stop diarrhea.
Pt will continue to have steatorrhea. |
|
|
Term
Stomach digestion:
Different nutrients leave the stomach at different rates:
___ leave first (regulated by CCK), foloowed by ___, ___, and ___.
Protein digestion begins with ___, which is converted to active ___ in the acidic stomach environment. |
|
Definition
CHO, protein, fat, fibrous foods
pepsinogen --> pepsin |
|
|
Term
Small intestine:
__-__% of the diet is absorbed
Appx __m long |
|
Definition
|
|
Term
Cell types in villi of intestine:
___: make up the top of the villi
___: digest and absorb nutrients
___: secrete mucus
___: secrete the hormones secretin, CCK, and GIP
___: secrete lysozyme and is capable of phagocytosis |
|
Definition
microvilli
absorptive cells
goblet cells
enteroendocrine cells
paneth cells |
|
|
Term
Carbohydrate digestion:
Mouth: ___, ___, __, or __ are the substrate for alpha-amylase
___ is the product of the reaction
Stomach:
Low pH inhibits action of alpha-amylase, so ___ takes over CHO digestion
Eventually, CHO are broken down into ___, wchih are absorbed by the small intestine and sent to the liver via portal circulation OR they end up as ___ which is excreted |
|
Definition
starch, lactose, sucrose, cellulose
maltose
pancreatic amylase
monosaccharides (glucose, fructose, galactose)
cellulose |
|
|
Term
| Why isn't cellulose absorbed by the small intestine? |
|
Definition
| alpha-amylase can only break down alpha linkages and cellulose is a beta linkage. thus, it is undigestable and is excreted |
|
|
Term
| What is lactose intolerance? |
|
Definition
| The lack of the disaccharidase that breaks down lactose in the small intestine and thus the pt is unable to digest lactose |
|
|
Term
| Explain the mechanism of absorption of monosaccharides by the cells of the small intestine including the SGLT and GLUT transporters |
|
Definition
At the apical membrane, Glucose and Galactose are taken into the cell via cotransporters with Na called SGLT. Fructose is taken in wihtout a cotransporter via GLUT 5.
At the basolateral membrane, the monosaccharides are transported from the cell into the blood wihtout cotransporters via GLUT 2's for each individual sugar
(slide 12 of ppt 3) |
|
|
Term
| How is ATP generated from CHO? |
|
Definition
Either:
Glycogen from liver broken down into glucose
OR
glucose from intestine
transported into muscle cell
Glucose broken down via glycolysis - produces 2 pyruvate + 2 ATP
It is then fermented into 2 lactic acids
OR
it is taken into the mitochondria via the ETC and used to make even more ATP via the citric acid cycle (something about acetyl CoA) |
|
|
Term
Protein digestion:
By ___ in the stomach, which converts it to __ & ___.
By pancreatic enzymes ___, ___, ___, and ___, which converts it into __ & ___.
By ___ in the small intestine, which converts it into ___, whcih are then absorbed and transported to the liver. |
|
Definition
pepsin (after it has been converted by pepsinogen) --> polypeptides and amino acids
elastase, carboxy-peptidase, trypsin, chymotrypsin __ . oligopeptides and amino acids
aminopeptidases --> amino acids |
|
|
Term
Activation of GI proteases:
1. Intestinal protein ingestion activates ___ to its active form, ___ by the brush border enzyme ___.
2. These activated ___, convert the other inactive precursors (various zymogens) to their active enzyme states. |
|
Definition
trypsinogen --> trypsin, via enterokinase
trypsin converts zymogens to their enymes v |
|
|
Term
| ___ break down proteins into amino acids and peptides |
|
Definition
|
|
Term
Digestion of protein begins in the stomach with the action of ___
Digestion of protein ends in the small intestine with pacreatic and brush-border ___ |
|
Definition
|
|
Term
Luminal protein digestion yields:
__% amino acids and
__% oligopeptides with 2-6 AA's |
|
Definition
|
|
Term
Absorption of Amino acids and peptides in the small intestine:
Na/AA cotransporters into small intestine epithelial cells are driven by the ___ gradient
Most ingested proteins are absorbed as di and tripeptides and are transported into the cell via a ___ cotransporter.
The di and tripeptides are then converted to amino acids via ___ in the cell and are then transported into the blood without a cotransporter |
|
Definition
Na
H+/oligopeptide cotransporter
peptidase |
|
|
Term
Disorders of protein digestion and absorption:
1. Deficiency of pancreatic enzymes:
- Ex: __ & ___.
- ___, ___, and ___ would be excreted in the feces as a result of the lack of enzymes.
2. Deficiency of Na-AA cotransporter
- ___: a genetic disorder with lack of this cotransporter |
|
Definition
chronic pancreatitis, cystic fibrosis
triglycerides, cholesterol esters, phospholipids
cystinuria |
|
|
Term
The major portion of fat digestion takes place in the ___ as a result of ___.
This process is more complicated than CHO/protein digestion because? |
|
Definition
small intestine, pancreatic lipases
more complicated bc fats have to first be converted into a water soluble product |
|
|
Term
Role of Stomach in lipid digestion:
1. Action of ___ breaks lipids into small droplets, increasing surface area for digestive enzymes.
2. Droplets are ___ by dietary proteins.
3. __ & ___ are responsible for 10% of triglyceride digestion.
4. The most important role of the stomach is to empty ___ into the small intestine at a controlled rate, rendering sufficient time for lipid digestion in the small intestine. Thus, ___ secretion depends on the contents of the food and the pH to control emptying rate. |
|
Definition
churning
emulsified
lingual and gastric lipases
controlled rate
CCK |
|
|
Term
Small intestine lipid digestion and absorption:
1. ___:
Produced by the liver and released into small intestine
Emulsify lipids
Solubilize products of lipid degestion to form a micelle
Remove waste products from the body by secretion into bile and elimination in feces.
2. ___ |
|
Definition
bile salts
pancreatic enzymes |
|
|
Term
|
Definition
|
|
Term
Pancreatic enzymes involved in lipid digestion:
1. ___: Hydrolyze triglycerides
- Activity is inhibited by bile salts at the lipid-H2O interface
- When bile salts are replaced by COLIPASE, this substance is active
- inactive pro-colipases secrete in pancreatic juic are activated by trypsin
2. ___: hydrolize cholesterol
- secreted as an active form of enzyme
3. ___:
secreted as an inactive form of pro-enzyme
- activated by trypsin in small intestin |
|
Definition
pancreatic lipase
cholesterol ester hydrolase
phospholipase A2 |
|
|
Term
Vitamins:
Are ___ & ___ for metabolic rxns.
Must be acquired from the diet and absorbed by the GI tract
2 types:
____: include B1, B2, B6, B12, C, biotin, folic acid, nicotinic acid, and pantothenic acid
--> absorption in the small intestine via Na-dependent cotransport mechanism, similar to glucose or AA
___: include Vit A, D, E, and K
--> absorbed via the same process as lipids |
|
Definition
co-factors and co-enzymes
water soluble
lipid soluble |
|
|
Term
Vit B12 absorption:
1. released from food via ___ action in the stomach
2. Free B12 binds to ___ secreted by salivary juice
3. IN the duodenum, pancreatic proteases degrade this substance and B12 is transferred to ___.
4. The B12-__ complex is resistant to degradative actions of enzymes and can be absorbed in the ileum. |
|
Definition
pepsin
R-protein
Intrinsic factor
B12-intrinsic factor complex |
|
|
Term
__% of fluid/electrolytes are absorbed in the small intestine
__% of fluid/electrolytes are absorbed in the colon |
|
Definition
|
|
Term
Mechanisms of trasnport of sodium in GI tract:
Na is primarily dependent on cotransporters with ___ & ___.
Thus, Na transport depends on the concentration of these solutes.
Absorbed sodium is rapidly exported from the cell via Na pumps - when a lot of Na is entering the cell, a lot of it is pumped out of the cell, which establishes a high ___ in the small intercellular spaces between adjacent enterocytes |
|
Definition
glucose and AA
osmolarity |
|
|
Term
Mechanisms of H2O transport in GI tract
H2O diffuses in response to the osmotic gradient established by ___ --- so into the intercellular space.
Most H2O absorption is ___ (through the cell) but some is ___ (between cells).
H2O and Na then both diffuse into the capillary blood within the ___. |
|
Definition
Na
transcellular, paracellular
villus |
|
|
Term
Large intestine activities:
Absorption of __ & __
Digestion and metabolism of ___ that wasn't digested yet.
No mammalian cell can digest ___, but bacteria in the large bowel can digest it.
Bacteria also synthesize __ & ___ in the bowel.
Bacterial ___ produces gases and organic acids. |
|
Definition
water and electrolytes
CHO
cellulose
Vit K and B vitamins (thiamin and riboflavin)
fermentation |
|
|
Term
| How does diarrhea result in Na and H2O being retained in the lumen of colon cells? |
|
Definition
| High flow rate of intestinal fluid in diarrhea causes increased K secretion resulting in hypokalemia, which results in Na and H2O being retained in the lumen |
|
|
Term
Pancreatic insufficiency
Zollinger Ellison syndrome
Cholestasis/bile salt deficiency
lack of brush border enzymes
nutrient digestion by bacterial overgrowth
All are causes of ___ |
|
Definition
|
|
Term
Celiac sprue - steatorrhea
gastroenteritis
crohn's disease
lymph obstruction
all are causes of ___ |
|
Definition
|
|
Term
| Lactose intolerance is a disease involving insufficient ___ digestion |
|
Definition
|
|
Term
4 types of diarrhea
1. As seen in the ileum resection
2. ingestion of poorly absorbed substrate (usually a CHO or divalent ion). ex is lactose intolerance
3. Ex: cholera. occurs when secretion of water into the intestinal lumen exceeds absorption.
4. E. coli is example |
|
Definition
decreased absorptive surface area
osmotic diarrhea
secretory diarrhea
intestinal infections |
|
|
Term
2 blood supplies to the liver
1. ___: drains blood from the GI tract and spleen to the liver. Brings O2-poor and nutrient rich blood. Thus, all nutrients are processed by the liver before being released back into the central veins.
2. ___: branch of the celiac trunk. Brings O2-rich blood. |
|
Definition
portal vein
hepatic artery |
|
|
Term
| Components of the hepatic triad |
|
Definition
Portal vein
Hepatic artery
Bile drainage duct |
|
|
Term
Liver lobules:
Each hepatocyte has a ___ in the middle of it
Bile produced by hepatocytes is released by ____ to be transported to ___ , which carry it to the liver.
___ make up the complex of "walls" radiating and bring blood in to the central vein. They are special liver capillaries where blood mixes and liver cells act. |
|
Definition
central vein
canaliculi, bile duct
sinusoids |
|
|
Term
___ cells are located in the sinusoids. The belong to the immune system and are used for ingestion of bacteria.
__ cells are located in the perisinusoid space along with the hepatocytes. They contain lipid droplets with Vit A. In inflammation, these cells become transformed to ___, which secrete collagen and extracellular matrix into the perisinusoidal space. This inflammatory response is partially responsible for ___ of the liver.
This structure facilitates rapid exchange of molecules |
|
Definition
Kuppfer cells
stellate cells (contractile phenotype), myofibroblasts (proliferative phenotype) = scarring |
|
|
Term
|
Definition
1. detoxification
2. carbohydrate metabolism
3. protein metabolism (albumin, prothrombin)
4. lipid metabolism (lipoprotein synthesis)
5. bile formation and secretion
6. blood detoxification and purification (remove old RBCs, degrade Hb to bilirubin, urea formation from ammonium) |
|
|
Term
CHO metabolism in liver:
Purpose: maintain glucose homeostasis at about __ mg/dl
___: synthesis of glucose from fats, AAs, and lactate. Uses non-carbohydrate substrate to produce glucose -- done during fasting.
___: breakdown of glycogen into glucose during fasting
___: formation of glycogen from glucose to store CHO in the liver as blood glucose level rises. Uses glucose to make glycogen. |
|
Definition
90
Gluconeogenesis
Glycogenolysis
Glycogenesis |
|
|
Term
| Why is it important to keep glucose levels steady? |
|
Definition
Glucose is the energy source for RBCs and renal medulla
Preferred energy source for brain |
|
|
Term
Protein and AA metabolism in liver
Sythesize ___ such as fibrinogen
Produce __ via ammonia (major fxn of the liver) - important for ___ metabolism. Important substrates for non-essentail AA such as tyrosine and cysteine and nucleic acids. |
|
Definition
plasma proteins
urea, nitrogen, |
|
|
Term
Lipid metabolism in the liver:
1. ___ synthesis to form bile salts
2. ___ & ___ production.
3. Used to generate ATP or ketone bodies - free fatty acids after a meal are used for energy
- could result in diabetic ketoacidosis |
|
Definition
cholesterol
triglycerides and VLDL |
|
|
Term
What are some ways our body uses cholesterol?
__% of body's cholesterol is endogenous |
|
Definition
cell membranes
vit D
hormones
myelin
bile salts
85% |
|
|
Term
| How does the body make cholesterol? |
|
Definition
|
|
Term
How do we get LDL in our diets?
How do we get HDL in our diets? |
|
Definition
LDL: trans and saturated fats
HDL: mono-unsaturated fats (olive oil, canola oil) & fiber |
|
|
Term
| What are some coagulation factors that the liver produces? |
|
Definition
fibrinogen, prothrombin, V, VII, IX, X, and XI
protein C, Protein S, antithrombin |
|
|
Term
| What are some fat soluble vitamins that the liver stores? |
|
Definition
| A (vision), D (Ca absorption), K (synthesis of clotting factors) |
|
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