GASTRO-INTESTINAL HORMONES Dr. Zahoor Ali Shaikh DR. ABDELRAHMAN MUSTAFA Department of Basic Medical Sciences Division of Physiology Faculty of Medicine Almaarefa Colleges

Endocrinal control of GIT Main hormones: Gastrin Secretin CCK Motilin Somatostatin GIP VIP

GASTRIN Site for secretion : G-cells in the stomach. Actions Stimulates the release of HCL and Pepsinogen in the stomach. Increases gastric motility. Increases ileal motility . Relaxes Ileocecal Sphincter. Induces mass movements in colon [because to help the contents moving through GIT on arrival of new meal in the stomach].

SECRETIN Site of secretion Secretin is released from small intestine when stomach acid contents come to duodenum. Actions It inhibits gastric emptying to delay the acid contents of stomach to enter in the duodenum. It inhibits gastric secretion. It acts on pancreatic duct to produce large volume of watery, NaHCO3 secretion. It stimulates the secretion of NaHCO3 rich bile in the liver by acting on the bile ducts.

CCK [Cholecystokinin] Site of secretion from the duodenum in response mainly to fat, to a lesser extent to protein products. Actions (i). Inhibition of motility and secretion (ii). Stimulates pancreatic Acinar cells to secrete pancreatic enzymes [amylase, lipase, Trypsinogen, Chymotrypsinogen]. (iii). It causes contraction of gall-bladder and relaxation of sphincter of Oddi.

MOTILIN Site for secretion It is polypeptide and secreted by entrochromaffin cells and Mo cells in the stomach, small intestine and colon. Actions It causes contraction of smooth muscles in the stomach and intestine. It level increases during inter-digestive state and controls GIT motility between the meals.

SOMATOSTATIN Site for secretion It is secreted by D-Cells in pancreatic islets and by similar D-cells in GIT mucosa. Actions Somatostatin inhibits secretion of Gastrin, VIP, GIP, Secretin and Motilin. Somatostatin secretion is stimulated by acid in the lumen of intestine. It acts probably in a paracrine fashion.

GIP [Glucose Dependent Insulinotorphic Peptide] Site for secretion GIP is released from the duodenum. Actions GIP causes release of insulin. Insulin causes uptake and storage of glucose. GIP – before it was called Gastric Inhibitory Peptide [this role is minimum].

VIP [Vasoactive Intestinal Peptide] Site of secretion VIP is found in nerves in the GIT. Actions It stimulates intestinal secretion of electrolytes and water. Other action – relaxation of intestinal smooth muscle including sphincters. Inhibition of gastric acid secretion. It potentiates the action of acetylcholine in salivary glands. VIP is also found in brain, blood, autonomic nerves.

REMINDER

REMINDER

References Human physiology by Lauralee Sherwood, seventh edition Text book physiology by Guyton &Hall,11th edition Text book of physiology by Linda .s contanzo,third edition