ABSTRACT
The pancreas has both exocrine and endocrine functions, carried out by distinctly different groups of cells. The endocrine portion is limited to small rounded clusters of glandular tissue, the islets of Langerhans, ca. 300 µm in diameter, that form <2% of the mostly exocrine (acinar) pancreatic mass, but nevertheless secrete two crucially important peptide hormones involved in blood glucose regulation, insulin and glucagon. There are about 106 islets scattered throughout the human pancreas, each constituting an independent secretory unit receiving a copious capillary blood supply via the gastroduodenal and superior mesenteric arteries, and draining ultimately through the splenic and superior mesenteric veins into the portal vein.
