The bile ductule represents the part of the biliary tree that is lined entirely by cholangiocytes.
The bile from the canal of Hering continues to flow into the intrahepatic bile ductule, which is lined entirely by cholangiocytes. Three-dimensional analysis of immunocytochemical-stained serial sections of the liver reveals that the canal of Hering often crosses the boundary of the lobule and becomes bile ductule in the periportal space (of Mall). The main distinction between the canal of Hering and the bile ductule is not its location within the lobule, but whether the structure is partially or completely lined by cholangiocytes.
Intrahepatic bile ductules carry bile to hepatic ducts.
The ductules have a diameter of about 1.0 to 1.5 m and carry bile to the interlobular bile ducts that form part of the portal triad (see Fig. 18.10b). These ducts range from 15 to 40 m in diameter and are lined by cholangiocytes that are cuboidal near the lobules and gradually become columnar as the ducts near the porta hepatis. The columnar cells have well-developed microvilli, as do those of the extrahepatic bile ducts and gallbladder. As the bile ducts get larger, they gradually acquire a dense connective tissue investment containing numerous elastic fibers. Smooth muscle cells appear in this connective tissue as the ducts approach the hilum. Interlobular ducts join to form the right and left hepatic ducts, which in turn join at the hilum to form the common hepatic duct (Fig. 18.15).
In some individuals, the ducts of Luschka are located in the connective tissue between the liver and the gallbladder, near the neck of the gallbladder. These ducts connect with the cystic duct, not with the lumen of the gallbladder. They are histologically similar to the intrahepatic bile ducts and may be remnants of aberrant embryonic bile ducts.
Extrahepatic bile ducts carry the bile to the gallbladder and duodenum.
The common hepatic duct is about 3 cm long and is lined with tall columnar epithelial cells that closely resemble those of the gallbladder. All of the layers of the alimentary canal (see page 569) are represented in the duct, except the muscularis mucosae. The cystic duct connects the common hepatic duct to the gallbladder and carries bile both main of common sphincter of main pancreatic duct major duodenal hepatopancreatic papilla ampulla (of Vater) sphincter of hepatopancreatic ampulla (of Oddi)
FIGURE 18.15 • Diagram showing the relationship of hepatic, pancreatic, and gallbladder ducts. The gallbladder is a blind pouch joined to a single cystic duct in which numerous mucosal folds form the spiral valve (of Heister). The cystic duct joins with the common hepatic duct, and together they form the common bile duct that leads into the duodenum. At the entry to the duodenum, the common bile duct is joined by the main pancreatic duct to form the hepatopancreatic ampulla (of Vater), and together they enter the second part of the duodenum. Sphincters can be found at the distal part of these ducts. The sphincters of the common bile duct (of Boyden), the main pancreatic duct, and the hepatopancreatic ampulla (of Oddi) control the flow of bile and pancreatic secretion into the duodenum. When the common bile duct sphincter contracts, bile cannot enter the duodenum; it backs up and flows into the gallbladder, where it is concentrated and stored.