Ultrastructure of hepatic sinusoids in sheep

The fine structure of the sheep hepatic sinusoid has been examined. Unlike that of most previously studied mammals, the sheep sinusoid has a continuous endothelial lining and a distinct basal lamina. Another unusual feature of the sheep sinusoidal endothelium is the presence of fenestrae closed by thin, single‐layered diaphragms. Between the basal lamina and the hepatic parenchyma, processes of perivascular connective tissue cells are seen in unusual abundance. Particles consistent in size with very low density lipoproteins are found on both sides of the basal lamina, but the mechanism of transport of these particles across the endothelial barrier is unknown.