The pancreatic duct is located where tubes meet that secretes digestive enzymes. This duct joins the cystic duct (which carries bile from the gallbladder) and forms a small chamber that opens into the duodenum. The cells of the pancreas are surrounded by many blood vessels into which they secrete hormones (glucagon and insulin) into the blood. Insulin regulates the use of glucose into all the body tissues except the brain. If the pancreas fails to produce insulin or secretes it in low quantities, the result is a serious disease called diabetes mellitus.