The secretions of the pancreas, called pancreatic juice, include various enzymes, including pancreatic amylase (digestion of starch), trypsin, carboxypepiydase, and chymotrypsin (proteases), as well as pancreatic lipase (digestion of fats). Sodium bicarbonate is also produced, making the pancreatic juice alkaline. This alkaline solution stabilizes the pH in the duodenum, thus providing an optimal environment for the action of these enzymes.
Pancreatic juice is produced in clusters of exocrine cells called acini. The remaining cells in the pancreas (about 1 percent of the total) also form clusters (pancreatic islets). These are the endocrine cells that produce the hormones insulin, glucagon, somatostatin, and pancreatic polypeptide.
Pancreatic juice collects in small ducts that merge to form two large ducts. The main pancreatic duct exits the pancreas and merges with the common bile duct from the liver and gallbladder. This combined duct, called the hepatopancreatic ampulla, then enters the duodenum by passing through the hepatopancreatic sphincter. A smaller, second duct that exits the pancreas, the accessory pancreatic duct, joins the duodenum directly.