Morphogenesis of intrahepatic bile ducts of the human fetus. Light and electron microscopic study.

Abstract

The development of the intrahepatic bile ducts of the human fetus was investigated by light and electron microscopy. Bile canaliculi with microvilli and junctional complexes are already found in the embryo of 7 mm. Some of them are of the intracellular type. At six to seven weeks, large bile canaliculi bounded by four to seven liver cells appear. Subsequently, bile canaliculi are formed predominantly between three to four adjoining liver cells and this arrangement persists throughout later fetal life. The early intrahepatic bile ducts develop around the portal vein as epithelial cell plates derived from the hepatic duct and the branches sprout from the epithelial cell plates in several different places. The epithelial cell plates are separated from each other by primitive connective tissue and they change into a complex network of bile ducts. Formation of the intrahepatic bile ducts is completed by three months. Biliary duct cells at the end of the developing bile ducts are thought to transform into liver cells. Therefore, at the ducts of Hering various transitional cells appear between biliary duct cells and liver cells. The fine structure of the developing liver cells and biliaryduct cells is also described.