Major duodenal papilla and its normal anatomy.

The major duodenal papilla (papilla of Vater) is the point where the dilated junction of the bile and pancreatic ducts (ampulla of Vater) enter the duodenum. The ampulla is surrounded by the sphincter of Oddi, which not only controls the flow of bile and pancreatic juice into the duodenum, but also prevents the reflux of duodenal contents, bile and pancreatic juice into the bile and pancreatic ducts.