Structural and ultrastructural pattern of the embryonic and early foetal human liver

With the aim of stressing the main steps which characterize the early development of the human foetal liver, fragments of hepatic buds of 7-12 weeks of pregnancy have been processed for light and scanning electron microscopy; Vial and Porter technique for isolated cells has been utilized too. The obtained results can be summarized as follows. At the 7th-8th weeks the hepatocytes show a globose shape, their surface is furnished with scattered and irregular evaginations and they are arranged in loose and narrow ribbons, separated by vascular spaces; the hepatocytes are tightly connected with haemopoietic cells, usually furnished with hyperchromatic nuclei. On the other hand, the hepatic parenchyma shows a compact pattern at the 11th-12th weeks. The hepatocytes have acquired a polyhydric shape and their faces are usually interlocked with the plasmatic membrane of the adjoining elements than in three fields: (a) the face projecting to the vascular walls with which they are going to form the Disse spaces; (b) the opposite side in which the membranes of neighbouring cells often appear spaced to line the primitive biliary canaliculi; and (c) the areas in which hemispheric and deep hollows of the hepatocyte surface hold haemopoietic elements. The obtained results demonstrate that the developing hepatic buds undergo deep structural changes, at level of the parenchyma and vascular system, in the studied period.