Structure of rat bile canaliculi as revealed by scanning electron microscopy

Bile canaliculi in the rat liver have been studied by scanning electron microscopy. They appear as half tubules carved out of the hepatocytes' surface. In several cases the bile channel bifurcates to form two or three long branches running on the same face of the cell. Therefore, by SEM it seems obvious that the same side of an hepatocyte may be used for bounding two or more bile canaliculi. Some bile canaliculi display a flexuous course and show lateral sacculations. Some of them are large and apparently similar to the short lateral branches of the bile canaliculus; others are smaller and arise obliquely from the subjacent cortical areas of the hepatocyte cytoplasm. These latter structures are best observed in stereo-views in which they appear as narrow intracellular projections bordered with a few microvilli, actually opening into the lumen of the bile canaliculus. The SEM results suggest that these sacculations probably correspond to short intracellular branches of the bile canaliculi. Zones of minimal distance (0.1 mu) between the space of Disse and the bile channel have been frequently observed. They are actually the zones where the intercellular clefts arising from the subendothelial space of Disse come into closet contact with the bile canaliculus and might serve as sites of simple diffusion of substances.