Normal and Abnormal Development of the Biliary Tree
The extrahepatic biliary tree forms direcdy from the embryonic bud of tissue off the foregut. The intrahepatic biliary tree forms out of the interplay between the early hepatic endodermal cells, the hepatoblasts, and the mesenchyme of the primitive liver. The connection between biliary tree and parenchyma has long been the subject of study. In the stereoptic depiction of normal liver anatomy by Elias in 1949,47 the biliary tree was seen to drain the hepatic parenchyma via tubular structures, cholangioles, emerging from deep within the hepatic lobule. In a light microscopy study of normal adult liver anatomy, Crawford et al found that isolated biliary ductular structures were actually readily observed in histological sections. Using a Masson-trichrome stain, about 1 intralobular bile ductule could be identified per portal tract. The mature biliary tree is supplied by a vascular plexus derived from the hepatic artery.