GI secretion and its regulation
6 important questions on GI secretion and its regulation
How is the secretion of saliva controlled?
How is saliva secretion regulated?
How is the acid in the stomach secreted?
- Acid secreted by the stomach is generated inside parietal cells by the reaction of CO2 with water, which is catalyzed by carbonic anhydrase (CA) and generates H+ and bicarbonate.
- H+ is transported actively into the lumen of the stomach by pumps in the apical membrane that use ATP to transport H+ out and K+ in.
- Bicarbonate is transported actively into the interstitial fluid through the basolateral membrane in exchange for Cl-.
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By what is the secretion of acid by the parietal cells stimulated?
What are the strongest influences on pancreatic juice secretion?
- CCK acts on acinar cells to stimulate enzyme secretion
- Secretin acts on duct cells to stimulate secretion of bicarnonate-rich fluid.
By what is the release of CCK and secretin mainly regulated?
- Secretin: the acidity of the duodenal contents. More acidity --> more secretin secretion.
- CCK: concentrations of protein digestion products and fat in the duodenum. Rises as chyme leaves the stomach.
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