Perineural epithelium: a new concept of its role in the integrity of the peripheral nervous system.

A multilayered, squamous-celled epithelial cell membrane covering the individual nerve fasciculi of the entire peripheral nervous system ( both voluntary and autonomic) including the sensory and motor end organs has been demonstrated in various species of animals, including man. This membrane is the direct continuation of the pia-arachnoid mater from the central nervous system. Functional significance of this membrane, especially as a diffusion barrier and as a protector of the peripheral nervous system, is briefly discussed.