exam 1

Question 1

Major GI hormones and enzyme functions

Answer 1

Major GI Hormones
1. Gastrin
Source: G cells in the stomach, duodenum, and pancreas.
Function: Stimulates the secretion of gastric acid (HCl) by the parietal cells of the stomach, promotes gastric motility, and growth of gastric mucosa. Gastrin release is stimulated by the presence of peptides and amino acids in the stomach.
2. Cholecystokinin (CCK)
Source: I cells in the mucosal epithelium of the small intestine.
Function: Stimulates the gallbladder to contract and release stored bile into the intestine, aids in the digestion of fats and proteins. CCK also stimulates the secretion of pancreatic enzymes and may have a role in satiety.
3. Secretin
Source: S cells of the duodenum.
Function: Stimulates the pancreas to release bicarbonate, neutralizing gastric acid entering the small intestine. Secretin also stimulates bile secretion and influences the rate of gastric emptying.
4. Glucagon-like peptide-1 (GLP-1)
Source: L cells in the ileum and colon.
Function: Enhances insulin secretion in response to high blood glucose levels, inhibits glucagon release, and slows gastric emptying to promote satiety.
Major GI Enzymes
1. Amylase
Source: Salivary glands and pancreas.
Function: Breaks down carbohydrates into simpler sugars like maltose and dextrin.
2. Pepsin
Source: Chief cells in the stomach.
Function: Initiates the digestion of proteins into smaller peptides; activated from pepsinogen in the presence of stomach acid.
3. Lipase
Source: Pancreas.
Function: Catalyzes the breakdown of fats into fatty acids and glycerol.
4. Trypsin and Chymotrypsin
Source: Pancreas.
Function: Further break down proteins and polypeptides into smaller peptides. They are released as inactive proenzymes (trypsinogen and chymotrypsinogen) and activated in the small intestine.
5. Lactase, Sucrase, Maltase
Source: Brush border of the small intestine.
Function: Break down disaccharides (lactose, sucrose, maltose) into monosaccharides (glucose, galactose, fructose), which can be absorbed by the intestinal cells.