Illustration of an islet of Langerhans (cluster of central cells) located in the pancreas (endocrine function of the pancreas). The beta cells (yellow) secrete insuline, the delta cells (purple) secrete somatostatine, the PP cells (blue) secrete pancreatic polypeptide, the alpha cells (pink) secrete glucagon. The islet is surrounded by pancreatic acini (beige), exocrine function of the pancreas, from which separate draining ducts merge to form the pancreatic duct (intralobular).