Islets of Langerhans

Known as the insulin-producing tissue, the islets of Langerhans do more than that. They are groups of specialized cells in the pancreas that make and secrete hormones. Named after the German pathologist Paul Langerhans (1847-1888), who discovered them in 1869, these cells sit in groups that Langerhans likened to little islands in the pancreas. There are five types of cells in an islet: alpha cells that make glucagon, which raises the level of glucose (sugar) in the blood; beta cells that make insulin; delta cells that make somatostatin which inhibits the release of numerous other hormones in the body; and PP cells and D1 cells, about which little is known. Degeneration of the insulin-producing beta cells is the main cause of type I (insulin-dependent) diabetes mellitus.

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pancreatic islets irregular microscopic structures scattered throughout the pancreas and comprising its endocrine part (the endocrine pancreas). They are composed of at least four types of cells: the alpha cells, which secrete glucagon; the beta cells, which are the most abundant and secrete insulin; the delta cells, which secrete somatostatin; and the PP cells, which secrete pancreatic polypeptide. Degeneration of the beta cells, whose secretion (insulin) is important in carbohydrate metabolism, is the major cause of type I diabetes mellitus. Called also insulae pancreaticae [TA], islands of Langerhans, and islands of pancreas.

Pancreatic islet (I), surrounded by acinar tissue. Blood vessels (V) and a small duct (D) are also shown.

Pancreatic islet in early type 1 diabetes mellitus; on the left side it has been infiltrated with T lymphocytes and beta cells are not seen, while on the right the remaining beta cells stain brown with antibody to insulin.