The main duct of the pancreas begins in the tail and runs the length of the gland, receiving numerous tributaries on the way. It opens into the second part of the duodenum at about its middle with the bile duct on the major duodenal papilla. Sometimes, the main duct drains separately into the duodenum.
The accessory duct of the pancreas, when present, drains the upper part of the head and then opens into the duodenum a short distance above the main duct on the minor duodenal papilla. The accessory duct frequently communicates with the main duct.