The developing human biliary system at the porta hepatis level between 29 days and 8 weeks of gestation: a way to understanding biliary atresia. Part 1

The developing biliary system in normal human embryos from 29 days to 8 weeks post-fertilization was studied. The primitive extrahepatic bile duct that originates from the embryonic hepatic foregut diverticulum is in contact with the hepatic anlage from the start of organogenesis and remains so throughout the gestational ages examined. The primitive extrahepatic bile duct maintains continuity with the ductal plate from which intrahepatic bile ducts are eventually formed. Contrary to long-held concepts of biliary development, no 'solid stage' of entodermal occlusion of the common bile duct lumen was found at any stage of gestation in the material investigated. Therefore, biliary atresia is not caused by incomplete vacuolization of the 'solid stage'.