L28 Flashcards
what are the components of gastric secretions
acid
pepsin
intrinsic factor
mucus
what are the functions of the acid in gastric secretion
protective role (kills bacteria)
denature proteins (chemical digestion)
optimum pH for many digestive enzymes (pepsin requires a low pH to be activated)
render fluid isosmotic (150 mM HCl - HCO3-
-neutralised part)
what is the osmolarity of the gastric secretions. why
200mOsmol
This is because of the bicarbonate in the stomach (this is here fore protection of the epithelial lining of the stomach)
what is the pH of the stomach
1
what is the main digestive enzyme in the stomach
pepsin
why do we need intrinsic factor
for absorption of vitamin B12
what is B12 important for
(DNA, red blood cells, pernicious anaemia)
what os pernicious anaemia
B12 effects the production of RBC
therefore if you are severally lacing in intrinsic factor it causes anemia
why is mucus an important gastric secretion
protects against acid and mechanical forces
makes the lining elastic
what are the 3 different functions anatomical regions of the stomach and what do they secrete
Lower esophageal sphincter and cardia = mucus and HCO3-
fundus and body = H+, intrinsic factor, mucus, HCO3-, pepsinogen, lipase
antrum and pylorus = mucus and HCO3-
NOTE: fundus and body secret lipase but there is no fat digestion until the intestine
where is gastrin secreted from and what is it secreted into
gastrin is secreted by the late part of the stomach (antrum and pylorus) into the BLOOD (its a hormone) which then causes acid secretion in the upper parts of the stomach (fundus and body)
what are the structures of the stomach
lumonal to interstitial
laminar propria (contains gastric glands)
muscularis mucosa
sub mucosa
muscularis externa
serosa
where are the gastric glands located
in the body of the stomach (in the lamina propria)
describe the structure of the gastric glands
gastric pit = opening
surface cells
mucus secreting cells
oxyntic/parietal cells
chief cells
enterochromaffin like cells (ECL cells)
what do surface cells secrete. why is that important
The surface cells produce bicarbonate which is important for protecting the epithelial lining from the acid
what do mucus cells secrete. why is that important
Mucus cells are important for making it elastic and to withstand the mechanical factors. They also protect againsted the acids
what do parietal cells secrete
acid and intrinsic factor
what do chief cells secrete
enzymes such as pepsinogen
what do ECL cells secrete
ECL cells release histomine which is important in the control of gastric acids secretion
Parietal cells and chef and ecl cells are in close proximity
why is this
for control of the parietal cells
what is the volume and composition of gastric secretions
2 - 3 litres per day
composition varies depending on eating or fasting
between meals what is the rate of gastric secretion
15-30 mL/hour
isosmotic fluid is secreted by surface cells. what is the composition of this
isosmotic solution with similar [Na+] as plasma but higher [HCO3-]
also mucus
about 200mOsmol
what happens to the volume of gastric secretion when we are eating
it is superimposed on basal secretion are much larger volumes of
secretion
produced at 150 mL/hour (5-10x higher)