Hepatic sinusoids of human liver samples obtained by surgical or needle biopsy were examined under the scanning and transmission electron microscopes (SEM and TEM). The surgically obtained tissues were perfused, by the use of a needle and syringe, with Ringer solution and successively with glutaraldehyde solution through the cut ends of blood vessels, while the needle biopsy pieces were perfused by directly puncturing the parenchyme.
Endothelial cells of hepatic sinusoids possessed thin and flat cytoplasm with two types of fenestrations which have already been demonstrated in laboratory animals: smaller ones (less than 0.1μm) occurring in clusters to form “sieve plates” and larger ones (0.5-2μm) intermingling among the former.
Kupffer cells were definitely distinguishable from the endothelial cells under the SEM and no graduations were found between either cell type. The Kupffer cell possessed voluminous cytoplasm covered with numerous filopodia, microvillous processes and lamellipodia.
In the space of Disse examined under the TEM, there were a number of attenuated cytoplasmic processes. Because of their contents in fat droplets, caveolae and microfilaments, they were identified as the processes of fat storing cells of Ito. A discontinuous basement membrane-like material was also recognized in the space of Disse.