Islets of Langerhans

Schematic representation of the anatomic relationships in an islet of Langerhans. The insulin-producing beta cells (in blue) are mostly in the center closest to the systemic blood supply from pancreatic arterioles and are surrounded by the glucagon-producing alpha cells (in orange). On the outside are the delta cells (in yellow), which make somatostatin, and the PP cells (in green), which make pancreatic polypeptide. Periportal blood flow within the islet is from beta to alpha to delta cells.