The Endocrine Pancreas

Abstract

The vertebrate endocrine pancreas consists of numerous aggregations of cells, the islets of Langerhans, composed of several cell types and exhibiting varying degrees of organizational complexity. In mammals, the islets are small (70–300 µ in diameter), ovoid aggregations of cells dispersed throughout the pancreatic exocrine tissue. Larger islets are located along major trunks and branches, and the intermediate and smaller islets are found further out along the vascular and ductal trees. These small endocrine organs are responsible for the elaboration and secretion of a number of hormones. Among them, insulin and glucagon are critical to the regulation of carbohydrate, fat, and protein metabolism, and ultimately to the maintenance of an appropriate blood glucose level essential for central nervous system function (see Chapter 18). Inappropriate secretion of any of the islet hormones may produce some metabolic derangement; the most familiar in the human is diabetes mellitus, which is associated with B-cell dysfunction.