Pancreas: A spongy, tube-shaped organ that is about 6 inches long and is located in the back of the abdomen, behind the stomach. The head of the pancreas is on the right side of the abdomen. It is connected to the upper end of the small intestine. The narrow end of the pancreas, called the tail, extends to the left side of the body. The pancreas makes pancreatic juices and hormones, including insulin and secretin. Pancreatic juices contain enzymes that help digest food in the small intestine. Both pancreatic enzymes and hormones are needed to keep the body working correctly. As pancreatic juices are made, they flow into the main pancreatic duct, which joins to the common bile duct, which connects the pancreas to the liver and the gallbladder and carries bile to the small intestine near the stomach. The pancreas is thus a compound gland in the sense that it is composed of both exocrine and endocrine tissues. The exocrine function of the pancreas involves the synthesis and secretion of pancreatic juices. The endocrine function resides in the million or so cellular islands (the islets of Langerhans) that are embedded between the exocrine units of the pancreas. Beta cells of the islets of Langerhans secrete insulin, which helps control carbohydrate metabolism. Alpha cells of the islets of Langerhans secrete glucagon, which counters the action of insulin.