Langerhans, islets of
- Irregularly shaped patches of endocrine tissue in the pancreas.The normal human pancreas has about one million of them. Beta cells, the most common islet cells, produce insulin to regulate blood glucose. (Inadequate production of insulin is characteristic of diabetes mellitus.) Alpha cells produce an opposing hormone, glucagon, which releases glucose from the liver and fatty acids from fat tissue; these favour insulin release and inhibit glucagon secretion. Delta cells produce somatostatin, which inhibits somatotropin (a major pituitary hormone), insulin, and glucagon; its metabolic role is not clear. Small numbers of another type of cell secrete pancreatic polypeptide, which slows down nutrient absorption. See also endocrine system.
* * *▪ anatomyalso called islands of Langerhansirregularly shaped patches of endocrine tissue located within the pancreas of most vertebrates. They are named for the German physician Paul Langerhans, who first described them in 1869. The normal human pancreas contains about 1,000,000 islets. The islets consist of four distinct cell types, of which three (alpha, beta, and delta cells) produce important hormones; the fourth component (C cells) has no known function.The most common islet cell, the beta cell, produces insulin, the major hormone in the regulation of carbohydrate, fat, and protein metabolism. Insulin is crucial in several metabolic processes: it promotes the uptake and metabolism of glucose by the body's cells; it prevents release of glucose by the liver; it causes muscle cells to take up amino acids, the basic components of protein; and it inhibits the breakdown and release of fats. The release of insulin from the beta cells can be triggered by growth hormone (somatotropin) or by glucagon, but the most important stimulator of insulin release is glucose; when the blood glucose level increases—as it does after a meal—insulin is released to counter it. The inability of the islet cells to make insulin or the failure to produce amounts sufficient to control blood glucose level are the causes of diabetes mellitus.The alpha cells of the islets of Langerhans produce an opposing hormone, glucagon, which releases glucose from the liver and fatty acids from fat tissue. In turn, glucose and free fatty acids favour insulin release and inhibit glucagon release. The delta cells produce somatostatin, a strong inhibitor of somatotropin, insulin, and glucagon; its role in metabolic regulation is not yet clear. Somatostatin is also produced by the hypothalamus and functions there to inhibit secretion of growth hormone by the pituitary gland.
* * *
Look at other dictionaries:
Langerhans islets — or Langerhans islands n. ISLETS OF LANGERHANS * * * … Universalium
Langerhans islets — or Langerhans islands n. ISLETS OF LANGERHANS … English World dictionary
Langerhans, islets of — Best 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… … Medical dictionary
Islets of Langerhans — is the area in which the endocrine (i.e., hormone producing) cells of the pancreas are grouped. Discovered in 1869 by the famous German pathological anatomist Paul Langerhans, the islets of Langerhans constitute approximately 1 to 2% of the mass… … Wikipedia
islets of Langerhans — or islands of Langerhans [läŋ′ər hänz΄] n. 〚after P. Langerhans (1847 88), Ger histologist〛 irregular groups of endocrine cells in the pancreas that produce the hormone insulin: their degeneration may cause diabetes mellitus * * * … Universalium
islets of Langerhans — or islands of Langerhans [läŋ′ər hänz΄] n. [after P. Langerhans (1847 88), Ger histologist] irregular groups of endocrine cells in the pancreas that produce the hormone insulin: their degeneration may cause diabetes mellitus … English World dictionary
islets of Langerhans — ► PLURAL NOUN ▪ groups of cells in the pancreas that secrete the hormones insulin and glucagon. ORIGIN named after the German anatomist Paul Langerhans (1847 88) … English terms dictionary
islets of Lang|er|hans — «LAHNG uhr hahns», the small scattered endocrine glands in the pancreas that secrete insulin. Also, islands of Langerhans. ╂[< Paul Langerhans, 1847 1888, a German physician and anatomist] … Useful english dictionary
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 … Medical dictionary
Langerhans cell — Not to be confused with the beta cells making up the islets of Langerhans. Langerhans cells are dendritic cells abundant in epidermis, containing large granules called Birbeck granules. They are normally present in lymph nodes, and can be found… … Wikipedia