1 Flashcards
Outline the functions of the stomach:
- To store and mix food
- Dissolve and continue digestion
- Kill microbes
- Secrete proteases
- secrete intrinsic factor
- activate proteases
- lubrication
- mucosal protection
What is the purpose of intrinsic factor?
It aids absorption of vitamin b12 in the last 12 inches of the ileum.
Outline the anatomy of the stomach:
Fundus
Antrum
Pyloris
Pyloric sphincter
What are the 4 main types of cell found in the stomach?
Mucous cells
Parietal cells
Chief cells
Enteroendocrine cells
……………… cells sit in adjacent connective tissues beneath the epithelium in the gastric fundus.
Enterchromaffin
Enterochromaffin cells secrete ………….
Histamine
What is the purpose of gastric acid secretion?
To help us to dissolve large chunks of food.
What do parietal cells produce?
Gastric acid and intrinsic factor.
The hydrochloric acid in the stomach is very strong at pH ……….
2
What is the concentration of H+ in the stomach?
[H+] > 150 mM
How much gastric acid is produced per day?
approx. 2l/day
Outline the steps in production of gastric acid:
IN PARIETAL CELL:
- H2O breaks down into OH- and H+
- Co2 + H2O -> H2CO3
- H2CO3 rapidly dissociates into HC03- and H+
- H+ produced here react with OH- (from breakdown of water) and regenerate H2O
- H+ ions from breakdown of H2O pumped into stomach lumen via H+/K+ATPase pump in luminal membrane
- 1K+ pumped into cell for every 1H+ pumped out ; this ensures there is no change in polarity in the cell
- K+ pumped into cell diffuse back out via K+ channels in plasma membrane
- HCO3- from breakdown of H2CO3 is secreted into capillary for exchange of Cl- ions
- Cl- enter stomach by diffusion through Cl- channels
- In stomach, H+ and Cl- react to form HCl
What enhances the forward rate of reaction?
The removal of the end product. The production and secretion of H+ are coupled.