Gastric secretion Flashcards
What is the function of the Lower oesophageal sphincter?
prevents reflux of food into the oesophagus
what is the function of the funds?
Responsible for temporary storage
Releases food into the body slowly
What is the function of the body of the stomach?
- production of Hcl by parietal cell
- production of pepsinogens by chief cellls
- protective action of mucous cell against breakdown of stomach layers
- production of intrinsic factor by parietal cells
What is the function of the antrum
mixing and grinding
Gastrin production
How is the Ph of the stomach maintained?
- C02 from the blood is transported into the epithelial cells
- C02 reacts with H20- action increased by anhydride enzyme
- produces bicarbonate ion which is very unstable so breaks down easily into H+ and HC03-
- H+ moves into lumen of stomach through protein kinases
- HCO3- moves back to blood in exchange for Cl- ions
- Cl- ions moves into the stomach lumen where they react with H20 to for HCL
- H20 follows movement of chloride ions
What is the Ph of the blood in comparison with the stomach lumen
Ph of blood slightly increases- 7.4
Ph of stomach = 2
what stimulates protein kinases and how
Gastrin and Ach increase the concentration of calcium in the cells and therefore protein kinases
Histamine binds to Gs receptors- stimulate AC receptors to convert ATP into Camp which in turn stimulates protein kinases
What inhibits protein kinases
Prostaglandins- bind to GI receptors- inhibit AC receptors- cause Camp to be converted into ATP
Why are protein kinases so important?>
Control K/H transport in production of HCL
How are parietal cells triggered to produce HCl in the cephalic phase
Neurocrine:
sight/smell of food- increases the activity of the vagus nerve- releases Ach
Endocrine:
increased activity of vagus nerve causes G cells to secrete gastrin
Paracrine:
Release of gastrin/ach triggers ECL cells to release histamine
How parietal cells triggered to produce HCl in the gastric phase
Neurocrine:
Distension of stomach due to arrival of food- increases vagus nerve activity- increases the release of aCH
Endocrine:
Peptides in the lumen trigger G cells to release gastrin
Paracrine:
increased secretion of Gastrin and ach causes ECL cells to release histamine
how are parietal cells inhibited in the cephalic phase?
Take away smell/sight of food-increases vagus nerve activity
how are parietal cell inhibited un gastric phase
decreased ph/increased Hcl- decreases release of gastrin
how are parietal cells inhibited in the intestinal phase
Acid in the duodenum causes the release of secretin and the splanchnic/enterogastric reflex
These decrease the secretion of gastrin
Fat and CHO in the duodenum cause the release of the gastric inhibitory polypeptide and therefor decreased secretion of gastrin
What are secretin/gastric inhibitory polypeptide/cck
what do they do?
Enterogastrones- hormones released in response to changes in the duodenum-decrease gastrin secretion
