Endocrine pancreas: mechanisms of insulin secretion by the β-cells; interactions among insulin, glucagon and somatostatin

Abstract

The endocrine pancreas is composed of the islets of Langerhans which comprise approximately two million clusters of cells dispersed within the acinar tissue of the exocrine pancreas. In the adult, the islets constitute between one and two percent of the pancreatic mass. The islets are composed of four endocrine cell types: α-cells which secrete glucagon, β-cells which secrete insulin, δ-cells which secrete somatostatin, and PP cells which secrete pancreatic polypeptide (Table 1).