gastric secretion Flashcards
what is the function of the fundus in the stomach ?
storage
what is the function of the body of the stomach ?
storage
mucus
HCL
pepsinogen
intrinsic factor production
what is the function of the antrum of the stomach ?
mixing/grinding
gastrin productio
what cells in the gastric area secrete mucous ?
mucous neck cells
what cells secrete pepsinogen ?
cheif cells (chief holds a can of pepsi)
what do parietal cells of the stomach produce ?
Hcl and intrinsic factor
how is gastric acid created ?
1- CO2 enters the parietal cell as a waste product
2- CO2 binds with H2O to produce HCO3 that is catalysed by carbonic anyhydrase
3- HCO3 immedietly dissociates to H+ and HCO3
4- H+ is transported out the cell at the HKATPase pump
5- HCO3 is exchanged for Cl- which then leaves at the apical membrane through a chloride channel
6- the osmotic gradient of the chlorine pulls water through tight junctions which combines with H+ and Cl- to create HCL gastric acid
how does gastrin control gastric acid secretion ?
gastrin binds to CCKB receptor
this releases Ca+ which activates protein kinase C
PKC increase HK ATPase pump
how does histamine control gastric acid secretion ?
binds to Gs H2 receptor which initiates adenyln cyclase to convert ATP - cAMP
cAMP then activates protein kinase A which increases HK ATPase pump activity
how does ACh control gastric acid secretion ?
binds to M3 muscarinic cholinergic receptors which activate PKC to increase HK ATPase activity
what is the cephalic phase of gastric acid secretion ?
sight smell, taste of food triggers the vagus nerve
vagus nerve stimulates Ach to increase parietal cell activity and also sitmulates G cells to produce gastrin and also increase parietal cell acitivty
presence of Gastrin/Ach activates ECL cells to produce histamine and increase parietal cell activity
what triggers the gastric phase of gastric acid secretion ?
distension of stomach (arrival of food)
peptides in the lumen
Gastin/ACh
how do we inhibit the cephalic phase in gastric acid secetion ?
stop eating
how do we inhibit the gastric phase in gastric acid secretion ?
the decrease in pH from gastric acid causes a negative feedback and inhibits gastrin production
describe the intestinal phase of inhibition of gastric acid secretion ?
acid in the duodenum triggers sphlancnic reflex and secretin release which decreases gastrin secretion and stimulation
fat/CHO in the duodenum stimulates the release of GIP which decrease gastric secretion and parietal HCl secretion
what are enterogastrones ?
hormones (secretin, CCK,GIP) released from gland cells in the duodenal mucosa that prevent gastric acid build up by inhibiting acid secretion and reducing gastric emptying (contract pyloric sphincter)
what pH converts pepsinogen to pepsin ?
pH <3 causes hydrolysis (inactive at a neutral pH)
what are the roles of gastric mucous ?
protects mucosal surface from mechanical injury
neutral pH (HCO3) protects from gastric acid corrosion and pepsin digestion
why is intrinsic factor important ?
binds with B12 and the complex is absorbed from the distal ileum to produce vitamin B12
