Biliary tract

The biliary tract, (biliary tree or biliary system) refers to the liver, gall bladder and bile ducts, and how they work together to make, store and secrete bile. Bile consists of water, electrolytes, bile acids, cholesterol, phospholipids and conjugated bilirubin. Some components are synthesised by hepatocytes (liver cells), the rest are extracted from the blood by the liver.

Bile is secreted by the liver into small ducts that join to form the common hepatic duct. Between meals, secreted bile is stored in the gall bladder, where 80%-90% of the water and electrolytes can be absorbed, leaving the bile acids and cholesterol. During a meal, the smooth muscles in the gallbladder wall contract, leading to the bile being secreted into the duodenum.

Structure

The biliary tract is the common anatomical term for the path by which bile is secreted by the liver then transported to the first part of the small intestine, also known as the duodenum. A structure common to most members of the mammal family, it is often referred to as a tree because it begins with many small branches which end in the common bile duct, sometimes referred to as the trunk of the biliary tree. The duct, the branches of the hepatic artery, and the portal vein form the central axis of the portal triad. Bile flows in the direction opposite to that of the blood present in the other two channels.