islands of Langerhans /lang″gərhanz/ [L, insula, island; Paul Langerhans, German pathologist, 1847–1888] , clusters of cells within the pancreas that produce insulin, glucagon, and pancreatic polypeptide. They form the endocrine portion of the gland, and their hormonal secretions released into the bloodstream are balanced, important regulators of carbohydrate metabolism. The islands of Langerhans are scattered throughout the pancreas; the beta cells, which secrete insulin, usually appear in the center of each of the lobules. Alpha cells secrete glucagon, and pancreatic peptide cells secrete pancreatic peptide. The cells the islands comprise are arranged in plates interspersed by capillaries. Also called islets of Langerhans.
