When the sphincter of Oddi is closed, newly synthesized bile from the liver is forced into storage in the gall bladder. When open, the stored and concentrated bile exits into the duodenum. This conduction of bile is the main function of the common bile duct. When a person is not eating, about 25% of the bile produced by the liver passes straight into the bile duct with the rest being redirected into the gall bladder. The hormone cholecystokinin, when stimulated by a fatty meal, promotes bile secretion by increased production of hepatic bile, contraction of the gall bladder, and relaxation of the Sphincter of Oddi. Although the Sphincter of Oddi surrounds both ducts, it also contains a separate sphincter for each of the two ducts that pass through it.