Cytoarchitecture of periendothelial cells in human cerebral venous vessels as compared with the scalp vein. A scanning electron microscopic study.

Three-dimensional cytoarchitectures of the periendothelial cells of human cerebral venous vessels as well as a scalp vein were studied by scanning electron microscopy after removal of extra-cellular connective tissue matrices with a KOH-collagenase digestion method. Postcapillary venules appeared covered with pericytes, while collecting venules had stellate periendothelial cells which formed a basket-like network around the vessel wall. As the size of the venous vessels increased, the stellate periendothelial cells became flat in shape and dense in arrangement. Although they had some characteristics similar to the smooth muscle cells in surface structure, no spindle-shaped smooth muscle cells were recognizable even in the superficial cerebral veins. On the other hand, the scalp vein was densely covered with spindle-shaped smooth muscle cells running circularly. These findings suggest that the cerebral venous vessels cannot constrict strongly as compared with the scalp vein, but probably regulate blood volume by mildly changing the caliber of the vessels.