The pancreas is a complex organ located deep in the abdomen that has many functions. It produces digestive enzymes, which drain through the pancreatic duct into the duodenum, which is the first part of the small intestine. Although this portion of the pancreas (the exocrine portion) can develop benign or malignant tumors, they are not specifically discussed here. The pancreas also has specialized cells which produce a number of endocrine hormones. The information to follow concentrates mostly on this "endocrine pancreas."
Only about 5% of the mass of the pancreas is composed of endocrine cells which are also called "islet cells" since they are clustered together like small islands. These cells secrete important hormones into the bloodstream. Some of these hormones are insulin, glucagon, gastrin, and vasoactive intestinal peptide (VIP).