Gastric Secretion Flashcards
5 constituents w/ physiologic functions
H ion, Pepsinogen, Mucous, Intrinsic factor, Water
Most important action of hydrogen ions in the stomach
Kills bacteria
2 functions of mucous in the stomach
Lubricates food and protects lining of stomach
2 areas of gastric secretion
Oxyntic: acid secretion
Pyloric: G cells
What do PPIs inhibit
H+/K atpase
How does chloride get into lumen in acid secretion
Via a difusión gradient
Goes into cell via secondary active transport
What is seen in a resting parietal cell
Tubulovesicles seen and a small intracellular canaliculus
How is an electrical gradient made in in oxyntic glands
By pumping chloride into the lumen
What prevents acid from getting out of the stomach
Gastric mucosal barrier (mucous and HCO3)
What ions go up in increased gastric flow rates
H, K and Cl (but cl always high)
What decreases in low flow rates
Sodium, H, and K
What do you see in pt’s w/ chronic vomiting
Hypokalemia and metabolic acidosis (due to rapid acid secretion)
Two fluids secreted in stomach
Oxyntic: HCl (predominates)
Non-oxyntic: HCO3
3 parietal cell stimulators
Ach, Gastrin, and Histamine
What receptors do ECL cells have? what gets released
Has gastrin receptors
Releases histamine
Histamine does what intracellularly?
cAMP increase via adenylcyclase
Gastrin does what intracellualr
IP3 mechanism
What stimulates the cephalic phase of gastric secretion
Vagus nerve
2 actions of vagal nerve in the cephalic phase
Ach stimulates parietal cells
GRP releases Gastrin from G cells
Does Ach release gastrin?
Yes, but indirectly (GRP direct mediator)
When is somatostatin released
When antrum pH drops below 3 to inhibit all gastrin release
2 main acid inhibitors
Somatostatin and secretin
Gastric secretion in response to a meal
pH of stomach contents goes up when food neutralizes, then begins to go down as more acid is secreted
Major effector of pepsin secretion
Vagal activity
What causes gastric ulcers?
Defective gastric mucosa
“low” acid secretion
What causes duodenal ulcers
too much acid secretion, not enough HCO3 to neutralize
