24: Extrahepatic Biliary Tree

Structure & Macroscopic Appearance

Cystic Duct

The cystic duct is about 4 cm long, and passes from the neck of the gallbladder to the common hepatic duct in the lateral border of the lesser omentum. It is accompanied by the vessels and nerves for the gallbladder. The cystic duct is notable for the spiral valve, a set of angular flaps that may prevent the flow of bile.

Common Hepatic Duct

The common hepatic duct is formed by the union of the right and left hepatic ducts, just beyond the porta hepatis in the lesser omentum. It is rapidly joined by the cystic duct to form the bile duct

Bile Duct

The bile duct (previously: common bile duct) runs from the union of the common hepatic duct and cystic duct. It runs inferiorly, posterior to the first part of the duodenum and anterior to the pancreas. It unites with the main pancreatic duct and then passes laterally to empty into the second part of the duodenum. This opening is the hepatopancreatic ampulla, surrounded by the sphincter of the bile duct.

Microscopic Structure

The outer layers of the ducts contain smooth muscle in various arrangements. The mucosa has a simple columnar epithelium with small mucous ducts present in the submucosa.