Shunting in intracranial microvasculature demonstrated by SEM of corrosion-casts

The use of methyl methacrylate corrosion-casts has made it possible to examine the intracranial microvasculature on a three-dimensional scale with the scanning electron microscope. By this means we have compared regions of four cerebral and cerebellar arteries among three domestic animal species. The results of this study suggest that there are from one to three different levels of interarteriolar anastomosis between branches of the same or adjacent vessels. In the horse and ox anastomoses were demonstrated (1) at the level of the precapillary arterioles, (2) along the arterioles, and (3) between small pial arteries. In the dog only the first-named anastomoses were evident in this study. These morphological characteristics may explain in part, the shunting mechanism by which hypoxia may be reduced among intracranial capillary networks.