The Gallbladder Stores and Concentrates Bile During the Periods Between Feeding

When there is little or no food in the intestinal lumen, the sphincter of Oddi, at the union of the common bile duct and duodenum, is closed. With this sphincter closed, bile cannot enter the intestine and is diverted into the gallbladder. The gallbladder epithelium absorbs sodium, chloride, and bicarbon­ate from bile; water is absorbed passively. Thus, in the gall­bladder the organic constituents of bile are concentrated, and the volume of bile is reduced. In species that have no gall­bladder, such as horses and rats, the sphincter of Oddi is apparently nonfunctional, and bile is secreted into the intestine during all phases of the digestive cycle.