The pancreas has two pancreatic ducts - the main pancreatic duct and the accessory pancreatic duct.

The main pancreatic duct (duct of Wirsung) goes through the pancreas parallel to its longitudinal axis. Therefore, its length matches the length of the pancreas. At the head of the pancreas, it unites with the common bile duct (Read more!), forming a Y-shaped configuration that further forms a short common channel that has a dilation called the hepatopancreatic ampulla (ampulla of Vater).

The ampulla of Vater opens in the posteromedial wall of the descending part of the duodenum via a slight mucosal elevation called the major duodenal papilla (papilla of Vater). This small opening is surrounded by a sphincter known as the hepatopancreatic sphincter (Oddi sphincter).

The hepatopancreatic sphincter (Oddi sphincter) is made of smooth muscle cells that regulate the flow of bile and pancreatic secretions into the duodenum. The muscle cells relax when food passes into the duodenum. But when there is no food, the muscle cells contract, and the opening closes. Besides the Oddi sphincter, the main pancreatic duct also has a separate sphincter (sphincter of the main pancreatic duct). These sphincters contribute to the anti-reflux system of the duodenal contents.

Besides the main pancreatic duct, the pancreas usually also has an accessory pancreatic duct. It is smaller and also opens in the posteromedial wall of the descending part of the duodenum. The opening of the accessory pancreatic duct is found above (approximately 0.8 inches (2 cm)) the major duodenal papilla and is called the minor duodenal papilla (papilla of Santorini). Sometimes, the papilla of Santorini is absent. If that happens, the accessory pancreatic duct joins the main pancreatic duct. Overall, the accessory pancreatic duct collects pancreatic juices from the head of the pancreas.

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Pancreatic ducts