The liver, gallbladder and small intestine are connected by a series of thin tubes called bile ducts. The bile ducts are part of the digestive system. The bile ducts and gallbladder are also part of the biliary system, or biliary tract.
The common bile duct is a very thin tube, about 10–12.5 cm (4–5 inches) long. A series of ducts come together to finally form the common bile duct:
The bile ducts within the liver are called intrahepatic bile ducts. These small ducts join together into larger ducts, ending in the left and right hepatic ducts. The right and left lobes of the liver are drained by these ducts. Information on intrahepatic bile duct cancer can be found in the liver cancer chapter.
The extrahepatic bile ducts are outside the liver. The extrahepatic ducts include the part of the right and left hepatic ducts that are outside the liver, the common hepatic duct and the common bile duct. (The cystic duct is also outside the liver, but cancers of the cystic duct are grouped with gallbladder cancers.)
The extrahepatic bile ducts may be further divided based on their location:
The extrahepatic bile ducts are part of a network of ducts that carry bile from the liver and gallbladder to the small intestine. Bile is a yellowish-green fluid made by the liver. Bile flows from the liver, through the hepatic ducts, into the cystic duct and to the gallbladder, where it is stored.
Bile helps digest the fat in foods. Bile is mainly made up of:
If the bile is not needed for digestion, it flows into the cystic duct and then into the gallbladder, where it is stored. When bile is needed to digest food, the gallbladder contracts and releases bile into the cystic duct. The bile then flows into the common bile duct and is emptied into the small intestine, where it breaks down fats.