4 Secretions of the stomach Flashcards
What do mucous neck cells secrete?
mucous
bicarbonate
What do parietal cells secrete?
Acid
IF
What do EC like cells secrete?
histamine
What do chief cells secrete?
pepsinogen
lipase
What do D cells secrete?
somatostatin
What do G cells secrete?
gastrin
What are the 4 main parts of the stomach?
fundus
corpus
antrum
pylorus
How does the parietal cell secrete acid?
H2O into the cell broken into OH- and H+ H+ out into lumen (H+/K+ transporter) OH- joins with CO2 to form HCO3- ALKALINE TIDE OUT Cl- channel into gut lumen forms with HCl in gut lumen
What are the 3 stimuli for acid secretion, their receptors, and the cell pathways?
ACh - M3 - Gq
Histamine - H2 - Gs
Gastrin - CCK(B) - Gq
What are G cells, and where are they located?
Secrete gastrin, in the anturm of the stomach, into the blood. It then stimulates acid production in other areas. sitmulated by ACh (Vagus nerve)
What is somatostatin?
inhibitor of acid secretion, secreted by D cells. binds to parietal cell receptors actin in a Gi mechanism, or onto ECL cells to inhibit histamine release.
inhibited by vagus nerve
What causes ACh release by the Vagus nerve?
stomach distension
What stimulates Gastrin release?
ACh
products of proein digesrtion stimulate G cells to release gastrin - positive feedback
What is secretin?
released by duodenal S cells
stimulated by fat and acid in the duodenum, it inhibits antral gastrin release and promotes somatostatin release
What is CCK?
cholecystokinin
preoduced by I cellsin the duodenum and jejenum is response to fat, decreasing parietal cell acid secretion
What is Omezaprole?
PPI
What is are Cimetidine and Ranitidine?
H2 receptor antagonists
What are the 4 stages of acid secretion?
basal phase - contemplative
cephalic phase - smell and taste
gastric phase - proper
instestinal phase - stimulated by partially digested stuff
What are pepsinogens stimulated by, what happens to them?
ACh stimulation of chief cells, they turn into pepsins when pH<5, works by autocatalysis
activation is irreversible at pH 7.2
What does the mucous layer do?
traps local HCO3-, maintaining a local pH = 7
What are prostglandins important for?
maintaining mucosal diffusion barrier
1 - inhibit acid secretion
2 - stimulate HCO3- secretion
3 - stimulate mucus secretion
What can H.Pylori cause in the antrum?
G cell gastrin hypersecretion
D cell somatostatin hyposecretion
ultimately hypergastrinaemia - ulcers
What can H.Pylori cause in the corpus?
reduced acid secretion and hypochlorhydria
What is intrinsic factor needed for?
Vitamin B12 absorption in the terminal ileum, produced by parietal cells
Without it it can cause pernicious anaemia
