The function of the pancreas is to make digestive enzymes, which digest food materials in the small intestines. In addition the pancreas also makes insulin, which controls the blood glucose levels.
The adult pancreas produces 10 - 20g of pancreatic enzymes in an active form. The acinar or gland cells of the pancreas carry out this work and pancreatic juice is activated when it enters the duodenum by the enzyme enterokinase. Secretion of enzymes by pancreatic gland cells is stimulated by the hormone cholecystokinin, which is released from the wall of the duodenum. In addition the hormone secretin, results in the pancreas making alkaline bicarbonate rich fluid, which neutralises acid from the stomach. It has been estimated that pancreatic ductal cells can each secrete their own volume of fluid in two to three minutes.
In addition the pancreas contains Islet of Langerhans the cells of which have four types of hormone secreting cells: A-cells secrete glucagon, B-cells secrete insulin, D-cells secrete somatostatin and PP-cells secrete pancreatic polypeptide. A failure of B-cells results in the condition of diabetes.
Pancreatic juice is a colourless thin fluid, which is either gin-clear or slightly opalescent. It contains large amounts of enzymes and all their precursors (zymogens). The enzymes have different categories of activity. Proteolytic enzymes such as trypsin, chymotrypsin and elastase cleave peptide bonds and digest proteins. Carboxypeptidases are also proteolytic enzymes, which digest proteins. On arrival of inactive pancreatic juice in the duodenum, enterokinase, which is produced by the brush border of the duodenum, converts trypsinogen to trypsin and releases trypsinogen activation peptide, TAP. Active trypsin activates all the other proteolytic enzymes, which then digest protein foods that are within the duodenum. The pancreas also produces lipase, which is activated in the duodenum and helps digest fat. Pancreatic amylase is responsible for digesting starch and other carbohydrates. The digestive power of activated pancreatic juice is phenomenal and should activated pancreatic juice make its way outside the gut, auto-digestion of the body's organs and structures can occur. It is for this reason that the complications of pancreatic surgery are so feared.