Pancreas: Islets of Langerhans and Diabetes Mellitus

H. Pancreas : The pancreas develops from endoderm and is both an exocrine gland (its digestive-enzyme role is covered under the digestive system) and an endocrine gland, its endocrine tissue organised into clusters called the islets of Langerhans, each holding four distinct hormone-producing cell types. Alpha (D) cells, about 20% of islet cells, secrete glucagon, which stimulates the liver toward glycogenolysis (glycogen breakdown), raising blood glucose level. Beta (E) cells, about 70%, secrete insulin, which stimulates the liver and muscles toward glycogenesis (glycogen synthesis), lowering blood glucose level. Delta (G) cells, about 5%, secrete somatostatin, which inhibits the release of both glucagon and insulin and also reduces gastric secretion, motility and digestive-tract absorption. PP (F) cells, the remaining roughly 5%, secrete pancreatic polypeptide (PP), which inhibits release of pancreatic juice. …