Histological and Structural Development of the Liver of Rats from the Embryonic Stage to Adulthood

Abstract

This study was conducted in the animal house of the College of Veterinary Medicine/Tikrit University. The study included (24) white rats and 4 male rats used for mating purposes only. They were divided into four equal groups, each group containing 6 samples of the liver of white rats (embryonic stage, one day old after birth, 7 days old after birth and adulthood stage). The study of the liver using the microscope showed that there was a gradual growth between the embryonic liver and the mature liver at the level of liver cells, blood sinuses, bile ducts, and liver lobes. The embryonic liver had simple squamous endothelium of the central vein, scattered hepatocytes, and hepatocyte aggregates of hematopoietic cell types, such as lymphocytes, red blood cells, and at times megakaryocytes. The hepatocyte packing associated with eosinophilic cytoplasm and lipid droplets, dilated sinusoids containing hematopoietic cells, white blood cell infiltration in the peripheral connective tissue. Seven days after birth, columns of hepatocytes were formed, branches of the portal vein and bile ducts were seen with the infiltration of white blood cells, and the isolated foci of hematopoietic cells and primitive bile ductules were identified.

Polygonal hepatocytes in the adult liver were radially organized around the central vein, and a well-integrated sinusoidal network was present, which harbored Kupffer cells, and this indicated structural and functional maturity. These data demonstrate the process of hepatic maturation of embryonic hematopoiesis into postnatal differentiation and vascular maturation, which leads to a functional structure with parenchymal architecture.