The peripheral nerves are solid white cords composed of bundles (fasciculi) of nerve fibers. Each nerve fiber is an axon with its coverings. The nerve fibers are supported and bound together by connective tissue sheaths at different levels of organization of the nerve. The whole nerve trunk is ensheathed by epineurium, each fasciculus by perineurium, and each nerve fiber by a delicate endoneurium. The toughness of a nerve is due to its fibrous sheaths, otherwise the nerve tissue itself is very delicate and friable.
Blood and Nerve Supply of Peripheral Nerves:
The peripheral nerves are supplied by vessels, called vasa nervorum, which form longitudinal anastomosis on the surface of the nerves. The nerves distributed to the sheaths of the nerve trunks are called nevi nervorum.