Chapter 42 Flashcards
The mucosa consists of these 2 things:
Surface epithelial cells and glands
With increasing rates of gastric juice secretion, [H+] concentration _____, and [Na+] concentration _____.
H+ increases, Na+ decreases
The proximal portion of the stomach secretes:
Acid, pepsinogens, intrinsic factor, bicarbonate, and mucus
The distal portion of the stomach secretes:
Gastrin and somatostatin
What are the 2 anatomical sections of the stomach?
Corpus and the antrum
What is the function of the stomach?
The stomach accomodates food, mixes it with gastric secretions, grinds it, and empties the food (now called chyme) into the duodenum.
What specialized structure does the parietal cell have?
Specialized tubulovesicular structure
What happens when the parietal cell is stimulated/activated?
It secretes acid
What channel/pump is responsible for the secretion of acid by parietal cells?
The H+/K+ pump
What three chemical signals (secretogogues) stimulate acid secretion from parietal cells?
- Acetylcholine
- Gastrin
- Histamine
How do the 3 secretogogues act physiologically on the parietal cell?
Either through the Ca2+ - Diacylglycerol (DAG) pathway or cAMP
What 2 cells secrete gastrin?
Antral and duodenal G-cells
Histamine is secreted by what specific cells in the stomach?
Enterochromaffin-like cells in the corpus section of the stomach
Somatostatin is secreted by which cells?
Gastric D-cells
What is the role of somatostatin?
Inhibits acid secretion
What other chemical signals aside from somatostatin inhibit acid secretion?
Several enteric hormones (enterogastrones) and prostaglandins
What are the 3 phases of acid secretion that is stimulated by a meal?
Basal state (no meal) Meal-stimulated phases: 1. Cephalic phase 2. Gastric phase 3. Intestinal phase
What 2 intramolecular pathways activate chief cells?
cAMP and Ca2+ pathways
What is the role of chief cells?
To secrete pepsinogens, which are the precursors to protein digestion
What is required for pepsinogen activation and pepsin activity?
Low pH
What does vagal innervation and irritation stimulate?
Stimulates gastric mucous cells to secrete mucin
What is mucin?
A glycoprotein that is part of the mucosal barrier
What do gastric surface cells secrete?
HCO3-
What chemical signals stimulates gastric surface cells?
Acetylcholine, acids, and prostaglandins
How does mucus protect the gastric surface epithelium?
By trapping an HCO3- -rich fluid near the apical border of these cells
Entry of acid into the duodenum induces what reaction?
The release of secretin from S cells
The release of secretin from S cells in the duodenum does what?
Stimulates the pancreas and the duodenum to secrete bicarbonate to neutralize the acid entering from the stomach into the duodenum
Gastric motor activity plays what roles?
Filling, churning, and emptying the stomach of food
Filling of the stomach is facilitated by what 2 concepts?
Receptive relaxation of the stomach and gastric accomodation (to the food)
The stomach churns the food up until what point?
Until the food particles are small enough to be gradually emptied into the duodenum
