Phys Gastric Secretion Flashcards
conc of HCl in stomach
approx 150 mN
5 products secreted by stomach
Hydrogen ion Pepsinogens Mucus IF Water
Purpose of IF
absorption of B12
Pepsinogen function
cleaves internal peptide bonds
3 acid purposes
anibacterial
activates pepsinogen to pepsin
denatures protein
what cells excrete acid?
what cells excrete pepsin?
what cells excrete IF?
parietal cells
chief cells & mucous cells
parietal cells
what is the only essential excretion of the stomach? What do you have to do after gastrectomy?
IF
administer B12
compare veinous and arterial gastric blood when secreting acid?
veinous is more alkaline
what enzyme allows formation of H+?
carbonic anhydrase (from CO2, OH-
relationship of Cl- in acid production
excreted passively after antiported vs HCO3-
what drives acid production in parietal cells?
NaKATPase, of course
where is HCl excreted in parietal cells?
in tubulovesicles, which become continuous with lumenal side in glands
3 stimuli that cause acid secretion & their intracellular messengers
vagus Ach (Gq IP3/Ca)
Gastrin (Gq IP3/Ca)
histamine (Gs cAMP)
2 inhibitors of HCl production & their intracellular messengers
somatostatin & prostaglandins
Gi, cAMP down
electrical potential outside cell on lumen side
80 mV
which way do H and Cl go vs gradients?
H+ down electrical gradient
Cl- up electrical & conc gradient
what do aspirin and ethanol do to potential difference between cell and lumen
Drop it synergistically
tonicity of gastric secretions?
isosmotic
how do gastrin and histamine relate in terms of acid secretion stim?
synergistic
why does GERD get worse at night?
acid secretion increases until midnight
peak acid secretion?
30 mEq/hr
how does interest in food relate to acid secretion?
directly - the more you like it, the more you eat.
what happens in absence of gastrin with vagal stimulation to parietal cells?
30% secretion anyway. (e.g. gastric bypass)
3 stimuli to G cells & result
vagal stimulation (distention of stomach or sensory, Ach)
local reflexes/distention (Ach)
Digested protein
produces gastrin
2 stimuli of ECL cells & result
Ach & Gastrin, histamine
3 areas of GI that inhibit acid secretion & mediators
Stomach, somatostatin
Duodenum: secretin, nervous reflex
jejunum & duodenum: GIP
how does acid secretion rate compare to pH & volume in stomach after feeding?
volume emptying goes fastest
pH follows
rate of acid secretion peaks later & is last to fall
why doesn’t acid get secreted before feeding?
low pH inhibits gastrin release
upon eating, 4 steps to acid secretion
vagal stim of parietal cells
pH goes over 3
gastrin secreted
higher acid secretion
how does H pylori effect damage on stomach? Result?
damage to mucosal barier by NH4+ synth using urease. reduced acid
PUD
acid levels in duodenal ulcers?
increased acid & pepsin
