Gastric secretion Flashcards
Structure of stomach
cardia fundus body - ruage antrum pylorus pyloric spinchter
functions of the stomach
storage mucus HCl pepsinogen intrinsic factor mixing gastrin
what do chief cells secrete
pepsinogens
what do parietal cells secrete
HCl
intrinsic factor
how is stomach lumen made acidic
CO2 enters Parietal Cell combine w H2O -> carbonic acid
dissociates, H ion pumped out (H K pump)
Cl comes into cell w transfer of HCO3
H2O + H + Cl = HCl
how is the hydrogen potassium ATPase pump regulated
Gastrin - from G cells, inc activity of pump, make lumen more acidic
Histamine
Acetylcholine - muscarinic receptor
^all stimulatory to pump
Prostaglandin - switches off mechanism
what does prostaglandin do to the ATPase H K pump
switches mechanism off, cAMP to ATP, reduce acidity
what stimulates the ATPase H K pump
gastrin
histamine
acetylcholine
what are the mechanisms responsible for control of gastric acid secretion
Neurocrine (vagus/local reflexes - ACh)
Endocrine (gastrin)
Paracrine (histamine)
what stimulates gastric acid secretion
- sight, smell, taste of food
- distension of stomach (food arival)
what inhibits gastric acid secretion
stop eating
increasing acidity, dec pH
acid in duodenum
- enterogastric reflex
- secretin release
- GIP release
what causes GIP release
Fat/CHO in duodenum, inhibit gastric acid secretion
what are Enterogastrones
hormones released from gland cells in duodenal mucosa
- secretin
- cholecystokinin (CCK)
- GIP (gastric inhibitory peptide)
why are enterogastrones release secretin, CCK, GIP)
in response to acid, FA or monogylcerides
act to prevent acid build up in duOdenum
- inhibit gastric acid secretion
- reduce gastric emptying
describe pepsinogen secretion
secreted by Chief cells
pepsins inactivated at neutral pH
Low pH <3 pepsinogen → Pepsin
same as HCl secretion, H K ATPase pump
what is a zymogen
inactive precursor, prevents cellular digestion
what is pepsin
stomach enzyme
digest proteins found in ingested food
what is the gastric mucus produced by
surface epithelial cells + mucus neck cells
what is the function of gastric mucus
protects surface
neutral pH → protect against gastric acid corrosion + pepsin digestion
what is intrinsic factor produced by and its function
produced by parietal cells
for B12 absorption
where is intrinsic factor/B12 complex absorbed
ileum
