Morphometric investigations of the pig developing liver during the prenatal period.

Quantitative changes in the developing liver of the pig embryo have been studied in the light microscope by stereological methods. Between days 18 and 112 of gestation the volumetric fraction of hepatocytes in the liver significantly increased and the volumetric fraction of blood vessels decreased. The haemopoietic cells reached the greater volumetric fraction about day 50 of gestation and thereafter their density declined. On the basis of the measurements of hepatic elements three different periods have been discerned. The first between days 18 and 39 when the differentiation of the liver takes place and the haematopoietic cells colonize it. The second is the period of intensive liver haematopoiesis between days 40 and 80. The third is from about day 80 to the birth when haematopoiesis declines and disappears and the volumetric fraction of hepatocytes significantly increases as a result of glycogen deposition.