Stereoscopic observation of the microvasculature of peripheral nerves.

The microvasculature of peripheral nerves in dog and human samples was studied by an injection replica scanning electron microscope (SEM) method. The three-dimensional relationship of epineural and intraneural vessels was well demonstrated by this method. Epineural vessels were made of both longitudinal arterioles and venules and also a close meshwork of capillaries. In the intraneural microvasculature, longitudinal arterioles and venules made up the perineural vessels, and grouped capillaries corresponded to the fine vasculature of intrafascicular vessels. Between epineural and intraneural vessels, there was little anastomosis but nutrient arteries ran through the epineural vasculature into the intraneural vessels. There was little interconnection of vessels among the intraneural vasculature. It was postulated that the close meshwork of the epineural layer can resist pressure from outside the peripheral nerves but that longitudinal venules seemed to be affected by pressure and tension at the localized area.