Anatomy and histology of the liver

The liver lobules are the structural and functional units of the liver. The lobule is surrounded by 6 portal tracts and centered on the centrolobular vein, which is a terminal twig of the hepatic vein. The portal vein ramifications in the portal tracts give off a series of branches between adjacent portal tracts, which in turn give rise to sinusoids draining blood towards the center of the lobule.

The liver parenchymal cell (hepatocyte) is a polygonal cell with a central nucleus. Hepatocytes are arranged in plates one cell thick with a sinusoid on either side, with a radial arrangement in the center of the lobule. The virtual cleft between the sinusoidal lining cells and the hepatocyte surface is the space of Disse. Fenestrated endothelial cells line the sinusoids. Kupffer cells, which are members of the mononuclear phagocyte system, bulge out on the luminal side of the sinusoids. Hepatic stellate cells (Ito cells) are perisinusoidal pericytes located in the space of Disse.

The portal tracts at the lobulary periphery are composed of connective tissue, ensheathing branches of the hepatic artery, portal vein, bile duct, and lymphatics. Ductules (or cholangioles) connect interlobular bile ducts with the lobular canaliculi, which are formed between adjacent hepatocytes.

Hepatocytes are polygonal in shape, with clearly outlined margins. The cytoplasm is granular and eosinophilic, usually rich in glycogen, with basophilic perinuclear aggregates of rough endoplasmic reticulum. The nucleus is centrally placed, with one or more nucleoli. Lipofuscin may occur as fine, light brown granules, mostly in centrolobular hepatocytes.