Gastric Phase Flashcards
What is the reason for H+ secretion in the stomach?
Killing microorganisms and conversion of pepsinogen to pepsin
What is the role of intrinsic factor?
intrinsic factor is essential for the absorption of vitamin B12 (which is essential for RBC formation)
What is the motor activity of the stomach for?
Mixing secretions of H+ and pepsin with the bolus of food
What is the effect of histamine release from ECL like cells
Histamine binds to nearby parietal cells and stimulates secretion of HCl
What is the general role of gastrin?
Gastrin is the “go” hormone- stimulates gastric acid secretion in the stomach and duodenum
What is the general role of somatostatin?
Somatostatin is the “stop” hormone- inhibits gastric secretion in the stomach, duodenum and pancreas
What two enzymes are released by the cells of the stomach?
Pepsinogens and lipase are both released from the fundus of the stomach
Where does mixing/grinding of the bolus of food occur in the stomach?
The antrum/pyloris.
The upper part, the fundus/body, is primarily a food reservoir/place where enzymes are secreted.
Where do gastric gland empty?
Into the gastric pits
What do chief cells secrete?
Pepsinogen
Under what environment are pepsins active?
acidic
What is secreted by enterochromaffin-like cells?
Histamine (a paracrine hormone)- it is the most powerful stimulator of HCl secretion (through the stimulation of parietal cells)
What is secreted by D cells?
Somatostatin- a powerful endocrine inhibitor of HCl secretion
What is secreted by G cells?
gastrin- an HCl secretagogue (indirect stimulation of parietal cells through ECL cells)
In healthy humans, what is the only essential component of gastric juice?
Intrinsic factors. All of the others are redundant
Where do the protons secreted by parietal cells come from?
CO2 and H2O –> H+ + HCO3-
How are protons secreted from parietal cells?
H+/K+ ATPase. It is an active process that transports both H+ and K+ across their chemical gradient
What drug blocks the H+/K+-ATPase?
Omeprazole (Prilosec)
How is Cl- secreted from parietal cells?
Facilitated diffusion through Cl- channels