The common bile duct begins at the junction of the common hepatic duct and the cystic duct and ends at the Ampulla of Vater in the second part of the duodenum. It carries bile from the liver and gallbladder to the gastrointestinal tract.
This small tube linking the liver and the duodenum is one of the most underestimated things in medical anatomy. The common bile duct has proven, so far, to be one of those tubes in the body that defy replacement, either by artificial tubes or stripped veins or any other material. It would not be fun trying to live without your bile duct - don't underestimate how important it is to drain bile...