The Stomach Flashcards
What is the stomach’s mechanical function?
Storage (stores food 3-4 hours) with aid of rugae, forms chyme partly through peristaltic movements
What is the stomach’s hematopoietic function?
Creates intrinsic factor which is necessary for Vit B12 absorption
What is the name of the condition where a deficiency in RBCs arises from a lack of B12?
Pernicious anemia
What is the stomach’s protective function?
Maintains a pH gradient that protects the gastric wall from pepsin and HCl via a thick mucus layer:
H+ ions (coming from the stomach) and HCO3- (produced by the surface cells) diffuse into the mucus layer and are neutralized: so the pH of the lumen can be maintained at ~1.5 but stays closer to 6.5 at the cell surface
What is the stomach’s digestive function?
Secretes gastric juice: HCl + pepsinogen + mucus and cellular secretions
Secretes proteolytic enzymes like pepsin and rennin/chymosin
What is the name of the glands in the stomach and what do they empty into?
Gastric glands that empty into the bottom of gastric pits
Describe the varying composition of the glands between different regions of the stomach
Cardia: mostly mucus-secreting glands (no enzymes)
Fundus and Body: Neck cells - mucus Parietal/Oxyntic: HCl Chief: pepsinogen Encodrine/G cells: Gastrin
Pyloric: mucus and G cells releasing gastrin
Which part of the stomach do gastric ulcers usually occur?
In the antrum and along the lesser curvature
What two things do neck cells secrete? What is the stimulus and the function of this secretion?
- Mucous: stimulated with irritation of the mucosa and provides a physical barrier between the lumen and epithelia
- Bicarbonate; secreted with mucus and buffers gastric acid to prevent damage to the epithelia
What two things do Parietal cells secrete? What is the stimulus and the function of this secretion?
HCl -> activates pepsin to kill bacteria
Intrinsic factor -> complexes with Vit B12 to permit absorption
Both are stimulated by Ach, histamine and gastrin
What does enterochromaffin-like cell secrete? What is the stimulus and the function of this secretion?
Histamine; stimulated by gastrin and Ach and stimulates gastric acid secretion
What two things do chief cells secrete? What is the stimulus and the function of this secretion?
Pepsionegn -> digests proteins
Gastric lipase -> digests fat
Stimulated by Ach, acid and secretin
What do D cells secrete, what is the stimulus and the function
Somatostatin; stimulated by acid in the stomach and it inhibits gastric acid secretion
What do G cells secrete, what is the stimulus and the function
Gastrin; stimulated by Ach, peptides and amino acids and stimulates gastric acid secretion
What does acid production in the parietal cell depend on the generation of? What enzyme helps generate this molecule?
Carbonic acid, carbonic anhydrase