The sphincter of Oddi (or hepatopancreatic sphincter) is a muscular valve that controls the flow of digestive juices (bile and pancreatic juice) through the ampulla of Vater into the second part of the duodenum. It is named after Ruggero Oddi. The sphincter of Oddi is relaxed by the hormone cholecystokinin (CCK) via vasoactive intestinal peptide (VIP).