digestive system 2
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23 terms
Terms | Definitions |
|---|---|
 mucosa | simple columnar, mucous cells secrete mucus |
| gastric glands/parietal cells | secrete HCL and intrinsic factor; convert CO2 and H20 into H2C03; |
| chief cells | secretes pepsinogen and gastric lipase |
| G cells | secretes the hormone gastrin into surrounding blood vessel |
| muscularis of stomach | 3 layers of smooth muscle |
| functions of the stomach | storage of food/large meal, digestion of food liquified into chyme, gastric secretions |
| production of HCL | produces acidic environment, softens/denatures proteins, prevents bacterial growth and spoilage of stored food |
| intrinsic factor | secreted by parietal cells, enhances absorption of vitamin B12 in small intestine |
| pepsinogen | secreted by chief cells, inactive form is zymogen; once its secreted into stomach lumen, it is activated at low PH into pepsin which digests proteins and breaks peptide bonds |
| gastric lipase | secreted by chief cells, begins digestion of lipids |
| mucosal cells | secrete a thick layer of mucus as a protective barrier on the surface of epithelial lining; is alkaline so its neutralizes pH across the surface, blocks digestive enzymes from damaging epithelial cells |
| Gastrin | secreted by G cells, targets the stomach, increases the secretion of gastric glands, and increases gastric motility |
| gastric motility | contractions of muscularis, mixes food with secretions through mechanical digestion and then empties into the small intestine |
| 3 phases of the stomach | cephalic, gastric, intestinal |
| cephalic phase | preparation to eat or currently eating; can be triggered by visual, smell, taste; small increase in gastric secretions, small increase in motility; under neural control from ANS and hypothalamus |
| gastric phase | food enters the stomach; there is a stretch in the stomach wall, chemoreceptors detect food; under parasympathetic fibers that stimulate increase motility of secretions, increase amount of gastrin; increased motility causes chyme to press against pyloric sphincter in waves |
| intestinal phase | inhibits stomach as food/chyme enters small intestine; stretches wall of small intestine, chemoreceptors detect food particles; hormones are secreted |
| GIP | secreted by small intestine; gastric inhibiting peptide, decreases motility and gastric secretions |
| secretin | inhibits gastric secretions; secreted by small intestine |
| CCK | cholecystokinin, decrease motlility; secreted by small intestine |
| neural response | enterogastric reflex; tightens pyloric sphincter, decreases gastric motility |
| intestinal inhibition | slows down stomach so that it empties slowly, may take 40 minutes to several hours to empty |
| absorption across stomach | limited to H20, ions, alcohol and aspirin |
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