Pancreatic duct

At a glance

English

Pancreatic duct

Latin (TA2)

Ductus pancreaticus

System

Digestive

Region

Abdomen

Side

Single, on the midline

About the pancreatic duct

Often named after Wirsung, the pancreatic duct is the principal outflow channel of the exocrine pancreas. It starts in the tail near the spleen and travels to the right through the body and neck, lying closer to the back of the gland than the front. Along the way it receives many short tributaries set at right angles to it, a herringbone pattern that drains each lobule, so it widens gradually as it nears the head.

In the head the duct bends downwards and backwards. There it comes alongside the lower end of the bile duct, and the two usually unite within the duodenal wall to form a short dilated channel, the hepatopancreatic ampulla (of Vater). This opens on the major duodenal papilla on the inner wall of the descending, second part of the duodenum. A ring of smooth muscle, the sphincter of the ampulla, together with smaller sphincters on each duct, controls flow and stops intestinal contents from washing back. In some people the two ducts open separately on the papilla rather than joining first.

The duct carries the alkaline pancreatic juice made by the acinar cells: a fluid rich in bicarbonate that neutralises acid arriving from the stomach, and a mixture of enzymes that break down proteins, fats and starches once they reach the bowel. Many of these enzymes travel in an inactive form and are switched on only inside the duodenum, which protects the gland from digesting itself.

Because the duct shares its outlet with the bile duct, a gallstone that lodges at the ampulla can block both, and bile or juice forced back up the pancreatic duct is a recognised trigger of acute pancreatitis. Narrowing or blockage by a tumour in the head of the gland makes the duct dilate upstream; on imaging, a calibre above about 3 mm in the head or 2 mm in the body and tail is usually treated as enlarged. Most pancreatic cancers arise from the cells lining the duct system.

Function and supply

Begins at

Begins in the tail of the pancreas from the joining of small lobular ducts and runs to the right through the body and neck into the head.

Ends at

Usually unites with the bile duct to form the hepatopancreatic ampulla, opening on the major duodenal papilla in the descending duodenum.

Function

Conveys pancreatic juice, with its digestive enzymes and bicarbonate, from the exocrine gland to the duodenum.

Blood supply

Its wall is supplied along its length by the pancreatic branches of the splenic artery and, in the head, by the pancreaticoduodenal arcades.