Biliary system

The organs and ducts by which bile is formed, concentrated, and carried from the liver to the duodenum (the first part of the small intestine). Bile is secreted by the liver cells and collected by a network of bile ducts that carry the bile out of the liver by way of the hepatic duct. A channel called the cystic duct branches off the hepatic duct and leads to the gallbladder where bile is concentrated and stored. Beyond this junction, the hepatic duct becomes the common bile duct and opens into the duodenum at a controlled orifice called the ampulla of Vater. The presence of fat in the duodenum after a meal causes secretion of a hormone, which opens the ampulla of Vater and makes the gallbladder contract, squeezing stored bile into the duodenum. The main disorders affecting the biliary system are gallstones, congenital biliary atresia and bile duct obstruction. (See also gallbladder, disorders of.)