Gut Endocrine Function - Anatomy & Physiology

Various regions of the Alimentary Tract secrete hormones which have various functions within the gastrointestinal tract itself, plus the liver, gall bladder and pancreas.

Many of the hormones act in a paracrine fashion, exerting their effect on cells close to the secretion site without travelling in the bloodstream.

Main hormones of the GIT

Hormone	Site of Secretion within GIT	Action
Cholecystokinin	Duodenum	Stimulates digestion of fat and protein by causing release of digestive enzymes and bile from the pancreas and gall bladder.
Gastrin	G-Cells in stomach and duodenum	Stimulates Parietal cells in the stomach to secrete HCl and Chief cells to secrete pepsinogen.
Gastric Inhibitory Peptide	Duodenumand Jejunum	Inhibits gastric motility and HCl secretion in the stomach, induces insulin secretion.
Ghrelin	Stomach and Pancreas	Increases food intake (by stimulating hunger) at the level of the hypothalamus.
Secretin	Crypts of Leiberkuhn in the Duodenum	Causes secretion of bicarbonate to buffer the pH of the chyme entering the small intestine. Also triggers insulin release.
Somatostatin	Gastric glands of the stomach	Inhibits release of gastrin and HCl from the stomach, inhibits secretin and cholecystokinin release from the duodenum and inhibits release of glucagon from the pancreas.