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23 terms

digestive system 2

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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