Three-dimensional organization of the hepatic microcirculation in the rodent as observed by scanning electron microscopy of corrosion casts

Abstract

The hepatic microcirculation was studied in three dimensions by scanning electron microscopy of corrosion casts. A methyl methacrylate casting medium was used which was formulated into a low viscosity mixture so that arterial, venous, and capillary divisions were filled and, hence, casted. Under injection conditions of constant flow and physiologic pressure, the casting medium appeared to distribute according to the intrahepatic vascular resistances. The vascular connections within the hepatic microcirculation and their extent could be easily assessed using this technique. The sinusoids were observed to be organized into dense, anastomosing capillary masses which were supplied by short inlet venules and terminal divisions of the distributing portal vein as well as by arteriolar capillaries. In some cases, the arteriolar capillaries connected with sinusoids at a point midway between the central and portal veins. The density of capillaries that was casted immediately adjacent to the portal areas varied extensively. Portal areas containing a paucity of capillaries appeared to define perivenular capillary thickets, the vessels of which radiated toward a centrally located collecting venule. The thickets followed the distribution of the hepatic venous divisions. These capillary masses produced patterns corresponding to the organization of the hepatic parenchyma. Increased permeability of the sinusoids in some areas was evidenced by leakage of casting medium from sinusoids into the spaces of Disse and Mall. Scanning electron microscopy of corrosion casts are useful in evaluating the three-dimensional organization of the normal hepatic microcirculation and could be applied to the study of perturbations that occur in the vasculature in pathologic conditions.