Comparison of the liver and biliary duct development in man and in the rat at the end of the embryonic period.

Hepatic and biliary structures present during embryonic Carnegie stage 23 were analyzed and compared in OFA-IOPS rat and human embryos. The group of embryos was composed of 3 rat specimens-crown rump length (CRL) 16 mm, age 16 days 5 hours post coltus- and of 1 human embryo- CRL 31 mm, age 57 days PC-. The specimens were submitted to serial histological sections with graphic reconstruction. In both species, the basic architecture of liver parenchyma was established including parenchymal cords or plates alternating with hepatic sinusoids. Veinous channels were clearly defined. The intrahepatic biliary system, referred as ductal plates (DP) developed into the periportal connective tissue while the portal spaces were not yet existing. DP was recognized either as a single layered cuboidal structure or as a double layered one dilated to form mature tubular ducts. The latter layout was more frequent in the rat. Except for gallbladder which is never present in the rat, similarity and presence of the same hepatic structure in both species at the end of the embryonic period (stage 23) suggest that the rat is a good experimental model for liver development and will be useful to understand the mechanism of congenital anomalies and specially the involvement of ductal plates in the congenital diseases of intrahepatic bile ducts.