Gastric Secretion Flashcards
what do mucous neck cells secrete?
mucus
what do chief cells secrete?
pepsinogen
what do parietal cells secrete?
> HCL
> intrinsic factor
what is the cellular composition of gastric glands?
> mucous neck cells
chief cells
parietal cells
what are the three mechanisms which control gastric acid secretion?
> neurocrine (vagus reflex)
endocrine (gastrin)
paracrine (histamine)
in the celiac phase for stimulating gastric acid secretion what 3 things act on parietal cells?
> acetylcholine from vagus nerve
gastrin from g-cells
histamine from ECL cells
what activates the vagus nerve in the celiac phase of stimulating gastric acid secretion?
sight, smell and taste of food
what stimulates the ECL cells to produce histamine I the celiac phase of gastric acid secretion?
gastrin and acetylcholine
in the gastric phase what activates the vagal/enteric reflexes?
distension of the stomach (arrival of food)
what activates G-cells to produce gastrin in the gastric phase?
peptides in the lumen
what activates ECL cells to produce histamine in the gastric phase?
gastrin and acetylcholine
in the gastric phase what cells does ACh, gastrin and histamine work on?
parietal cells
what inhibits gastric secretion in the cephalic phase?
cessation of eating which causes a decrease in vagal activity
what mechanisms inhibit gastric secretion in the gastric phase?
a decrease in pH creates a decrease in gastrin production
in the intestinal phase what is the effect of acid in the duodenum?
enterogastric (splanchnic reflex) and secretin release
= decrease in gastrin secretion and gastrin stimulation of parietal cells
what is released in response to fat in the duodenum?
GIP
what is the effect of gastrin release?
gastrin secretion and parietal HCl secretion
name some enterogastrones
> secretin, cholecystokinin, GIP
what releases enterogastrones?
gland cells in the duodenal mucosa
what are enterogastrones released in response to?
> acid > hypertonic solutions > fatty acids > monoglycerides in the duodenum
what to enterogastrones work to prevent?
further acid build up in the duodenum
what two strategies do enterogastrones use to prevent acid build up in the duodenum?
> inhibition of gastric secretion
> reduced gastric emptying (inhibition of motility/contraction of pyloric sphincter)
what secretes pepsinogen?
chief cells
what is zymogen?
inactive precursor to pepsinogen that prevents cellular digestion
what inactivates pepsinogen?
neutral pH
what produces gastric mucus?
surface epithelial cells and mucus neck cells
what does mucus protect the surface from?
> mechanical injury
gastric acid corrosion
pepsin digestion
what is the only non-compensated function of the stomach?
intrinsic factor secretion
what is intrinsic factor required for?
vit. b12 absorption
what can a defect in vit. 12 absorption lead to?
pernicious anaemia - failure of erythrocytes maturation
describe how carbonic acid is created in gastric glands
co2 enters the cell and combines with h2o creating carbonic acid.
what channel is H+ ion pumped out through?
potassium channel into the lumen
what membrane is carbonate pumped out of?
the basolateral membrane
how does water enter the lumen of the stomach?
through the para-cellular pathway
describe what happens in the cell when gastrin binds to it’s g protein coupled receptor
the activation of the receptor causes a rise in calcium that activates protein kinase that causes an increase in H ions being pumped by the proton pump into the stomach lumen
describe the histamine receptor used in gastric secretion control
it is a unique g protein coupled receptor: H2
what do prostaglandins inhibit when they bind to receptors of the stomach?
cAMP
what is the effect of prostaglandin binding to their receptors in the activity of the proton pump?
it causes decreased activity of the proton pump
