The ampulla of Vater, also known as the hepatopancreatic ampulla,or as Hepatopancreatic duct is formed by the union of the pancreatic duct and the common bile duct. The ampulla is specifically located at the major duodenal papilla.
The ampulla of Vater is an important landmark, halfway along the second part of the duodenum, that marks the anatomical transition from foregut to midgut (and hence the point where the celiac trunk stops supplying the gut and the superior mesenteric artery takes over).
Various smooth muscle sphincters regulate the flow of bile and pancreatic juice through the ampulla: the sphincter of the pancreatic duct, the sphincter of the bile duct, and the hepatopancreatic sphincter (Sphincter of Oddi).
The sphincter of Oddi controls the introduction of bile and pancreatic secretions into the duodenum, as well as preventing the entry of duodenal contents into the ampulla.