hormonal control of digestion Flashcards
What are the two main mechanisms regulating digestion?
Extrinsic mechanisms and intrinsic mechanisms.
What do mechanoreceptors respond to in the GI tract?
Presence/volume of ingested material.
What do chemoreceptors respond to?
Composition of ingested material.
What is the primary function of gastric mucosal epithelium?
Secretion of gastric juices.
What are the two types of secretion from gastric glands?
- Exocrine
- Endocrine
What does the gastric mucosal epithelium consist of?
Entirely of secretory cells.
What do enteroendocrine cells secrete?
Gastrin.
Where are enteroendocrine cells mainly found?
Gastric glands of pyloric region (antrum).
What is the primary secretion of parietal cells?
Hydrochloric acid (HCl).
What is the pH level of gastric contents due to HCl?
1-2.
What is the role of HCl in digestion?
- Breaks down connective tissue
- Activates pepsinogen
- Provides optimal conditions for pepsin
- Defense against microorganisms.
What substance produced by H. pylori neutralizes stomach acid?
Ammonia.
What is the function of the proton pump H+-K+-ATPase?
Exchanges H+ for potassium at the luminal surface.
What type of cells secrete pepsinogen?
Chief cells.
Pepsinogen is activated to pepsin at what pH level?
Lower than 3.5.
What protects the stomach from autodigestion?
- Mucus secretion
- Tight junctions between epithelial cells.
What stimulates the secretion of gastrin?
- Partially digested food
- Vagal reflexes.
What is Zollinger-Ellison syndrome caused by?
A gastrin-secreting tumor (gastrinomas).
What are the three phases of gastric secretion regulation?
- Cephalic phase
- Gastric phase
- Intestinal phase.
What hormone inhibits gastric secretion during the gastric phase?
Somatostatin.
What is the effect of high [H+] on D cells?
Stimulates secretion of somatostatin.
What is the function of somatostatin?
- Inhibits intestinal motility
- Inhibits gastric gland secretion.
What are the main cell types in the small intestine?
- Villous absorptive cells
- Goblet cells
- Enteric endocrine cells
- Stem/progenitor cells
- Paneth cells.
What is the role of goblet cells in the small intestine?
Secrete mucin, a major component of mucus.
What do Brunner’s glands secrete?
Mucus-rich bicarbonate.
What does GIP do in the digestive process?
Inhibits gastric H+ secretion.
The secretion of which hormones acts on accessory organs?
- Secretin
- CCK.
