Why is the pancreas both an endocrine and exocrine gland?

Endocrine organs release their products (usually hormones) directly into the blood. The pancreas contains islets of Langerhans which are made up of alpha and beta cells. Beta cells secrete insulin and alpha cells secrete glucagon. The islets of Langerhans monitor blood glucose concentration. Insulin and glucagon are hormones that help maintain a healthy blood glucose concentration.

Exocrine organs release secretions through a duct. The pancreas is an exocrine gland because nervous or hormonal stimulation causes pancreatic secretions to be released into the duodenum through a duct. The secretions are alkaline and contain enzymes such as lipase, amylase and trypsin. They aid digestion.