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54 Cards in this Set
- Front
- Back
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Where in the gut is gastrin primarily produced?
CCK?
Secretin? |
Gastrin - antrum of the stomach
CCK - small intestine
Secretin - small intestine |
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What effect does gastrin have on secretion and motility of the stomach?
CCK?
Secretin? |
Gastrin - Stimulates both
CCK - inhibits both
Secretin - inhibits both |
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What are the functions of the stomach? (3) |
- Store food - Initiate protein digestion - Kill bacteria |
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What range of volumes does the stomach have? |
50-100 mL to 2000 mL |
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How long can food remain in the stomach unmixed? |
~1 hour |
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What type of molecules is the last to digest? |
Fats (because they float to the top) |
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What is receptive relaxation? |
Upon swallowing, the gastric smooth muscle reflexively relaxes and decreases in pressure before food enters the stomach |
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What cranial nerve mediates receptive relaxation?
What NTs are involved? |
CN X
NO, VIP, DA |
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What is antral-pyloric systole?
What is the rate in the fed state? |
Peristalsis of the stomach to churn chyme and move it towards the pylorus.
4/min |
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What hormone increases the rhythm of the BER in the stomach during the fed state? |
Gastrin |
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Where are the interstitial cells of Cajal in the stomach? |
Longitudinal layer of muscle along the greater curvature of the stomach |
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How is gastric output measured? |
GO = BER x SV |
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What volume of the stomach's contents leads to faster emptying? |
Large volume |
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When the stomach is small, what is the rate of emptying?
When it's large? |
small = 2 mL/min
large = 20 mL/min |
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Besides small volume, what also slows the rate of stomach emptying into the duodenum? (3) |
- High osmotic pressure (saltiness) - High fat content - High protein content |
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How small must a particle be to still pass through a constricted pyloric sphincter by sieving action? |
0.2mm |
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Why does high osmolarity chyme empty into the duodenum slowly? |
To not overwhelm intestines with hypertonicity |
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If someone swallows a coin, will it move with food chyme into the duodenum? |
No, only when the stomach is empty |
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In what part of the stomach is most of the HCl generated? |
Body |
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What part of the stomach produces the most mucus? |
Antrum |
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What part of the stomach has most of the G-cells? |
Antrum |
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Are stomach secretions necessary for digestion? |
No (but they help) |
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Besides sterilizing chyme and denaturing proteins, what other function does HCl have in the stomach? |
Solubilizes iron |
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What molecule does the stomach secrete to sequester Vitamin B12?
What cell releases it? |
Intrinsic factor
Parietal cells |
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What is the tonicity of gastric secretions in the post-prandial state?
Fed-state? |
Post-prandial: Hypotonic
Fed: eutonic |
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How does K+ content of gastric secretions compare to plasma? |
There is always more K+ in gastric juice than in plasma |
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When do goblet cells secrete mucus to the lumen of the stomach?
Mucus neck cells |
Goblet cells - continuously
Mucus neck cells - only in fed state |
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What do ECL cells secrete in the stomach secrete? (2) |
Histamine and serotonin |
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What does serotonin in the stomach due? |
Cause nausea and vomiting |
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From what cells does somatostatin come? |
D-cells of the pancreas (delta cells) |
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What ion does the parietal cell bring into the stomach in exchange for releasing hydrogen ion? |
K+ |
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What enzyme in parietal cells helps produce acid? |
Carbonic acid |
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What happens to bicarbonate in the parietal cell once hydrogen ion has been secreted? |
It leaves via capillaries to the liver. |
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How is the bicarbonate moved out of parietal cells into the basolateral side? |
Cl-/HCO3- antiporter |
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If the pancreas must produce bicarbonate, what biproduct must it then deposit into the blood? |
H+ |
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What occurs to the bicarbonate in the blood leaving the stomach via capillaries? |
It is neutralized by the acidic blood coming from the pancreas before it enters hepatic circulation |
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What keeps the potassium level high inside the parietal cell? |
Na+/K+ ATPase |
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What is the most effective method to block acid secretion? |
Block the H+/K+ antiport ATPase on the parietal cell |
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What receptors are on the parietal cell?
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Gastrin - Promotes acid secretion Histamine - Promotes acid secretion Acetylcholine - Promotes acid secretion Somatostatin - Inhibits acid secretion |
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In the fasting state, where do the H+/K+ ATPases predominate? |
In vesicles inside the parietal cells |
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When acid promoting receptors are stimulated, what happens to the vesicles holding H+/K+ ATPases in the parietal cells? |
Those vesicles fuse with the apical plasma membrane |
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What second messenger does Acetylcholine use?
Histamine?
Gastrin? |
Ach - Ca++
Histamine - cAMP
Gastrin Ca++ |
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What effect does histamine have on acid secretion in parietal cells? |
It potentiates the actions of gastrin and acetylcholine |
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What feedback system inhibits gastrin release? |
Acidity of the stomach |
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What positive feedback system in the lumen of the stomach stimulates gastrin secretion? (2) |
Distension and amino acids |
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At what pH does HCl secretion decrease?
At what pH does it stop? |
decreases at <2.5
stops at 1.0 |
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What intestinal hormone class inhibits gastric secretion and motility when fat is present in the duodenum? |
enterogasterone |
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What 5 intestinal hormones slow down stomach function? |
- Somatostatin - CCK - Secretin - Enterogasterone - GLP-1 |
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What two drugs are readily absorbed by stomach mucosa? |
Aspirin and alcohol |
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What happens to salivary amylase in the stomach? |
It is deactivated |
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What makes gastric mucus alkaline? |
bicarbonate |
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What is the turnover of parietal and chief cells? |
3 days |
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What effect do prostaglandins have on gastric secretions? |
Inhibits them
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What effect do bile salts have on the stomach lumen? |
Damaging effect |
