Gastric Secretion Flashcards
role of chief cell
secrete pepsinogens
what is a zymogen
an inactive precursor to an active enzyme or substance e.g. pepsinogen –> pepsin
cells that secret HCl
parietal cells
secretions of parietal cells
HCl and intrinsic factor
what is intrinsic factor important for
transport of vit B12
mucus is secreted by what cells type in the gastric gland
surface and neck mucous cells
production of stomach acid requires entry of what two substances into the cell
Cl and CO2
in stomach acid production what is released back into the blood
bicarbonate (HCO3)
pH of stomach acid
<2
what moves across the leaky tight junctions of stomach epithelium as stomach acid is made
water
3 substances that stimulate gastric acid secretion
gastrin, histamine and acetylcholine
where does gastric acid production occur
in parietal cells
how do gastrin, histamine and ACh stimulate gastric acid production
by stimulating the K/H primary active pump
mechanism of histamine on acid secretion
- unique receptor when in gut stimulates a G protein coupled to AC
- AC makes ATP to cyclic AMP
- cAMP acts on proteins kinases to stimulate K/H pump
how do prostaglandins inhibit secretion
turns off AC thus stopping cAMP being made
neurocrine control gastric secretion
ACh
endocrine control of gastric secretion
gastrin
paracrine control of gastric secretion
histamine
what cells secrete histamine
ECL cells
what substances stimulate ECL cells to release histamine
gastrin and ACh
what stimulates G cells to release gastrin
- peptides in stomach lumen
2. vagus nerve
what initial input triggers the vagal and enteric reflexes for gastric secretion
food in stomach causing distension
presence of acid and fat has what effect on gastrin and HCl secretion
inhibition
reflex that communicates acid in duodenum to stop gastrin and hence gastric secretion
enterogastric (splanchnic reflex)
