Illustration of tissues of the pancreas. Most of the pancreas is involved in secreting enzymes from clusters of gland cells (pancreatic acini), seen here coloured pink. However, the pancreas has two functions: secretion of digestive enzymes, and the production of hormones. Internal to the acini are yellow groups of cells named Islets of Langerhans. These are involved in the endocrine function of hormone production. Here, alpha cells (red) are involved in secreting glucagon. The numerous beta cells (yellow) secrete insulin. And delta cells (blue) secrete a hormone, somatostatin. The pancreas lies near the duodenum. A low production of insulin by the pancreas causes diabetes.