Anatomy of finfish and shellfish

Unit 9 - Endocrine system

9.2.6. Islets of Langerhans
Islets of Langerhans, also called islands of Langerhans, irregularly shaped patches of endocrine tissue located within the pancreas of most vertebrates. 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.Within the pancreas of higher forms of sharks,islets of Langerhans develop from the tubules of the otherwise called digestive gland.islets tissue in the actinopterygian fishes tend to be concentrated.There is usually one islet or sometimes two large islets in the region of the bile duct.in agnathan fishes pancreatic islets have been observed in the lamprey but not in the Hag fish.The endocrine pancreas is present in most fish as islet of Langerhans and is associated with the exocrine pancreas. In some species the islets are very large and may be grossly visible (Brockman bodies). During the spawning season the size and number of islet will increase in some fish.