digestive system 2

23 terms by linzard09

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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

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