Figure 1. Structure of Peripheral Nerves. Peripheral nerves are composed of several fascicles of endoneurium, each enveloped by perineurium and bound together by loose connective tissue, the epineurium. Each fascicle of endoneurium contains up to several thousand axons. Blood is supplied to the endoneurium by a network of capillary-like microvessels derived from arterioles and venules in the epineurium, which in turn are branches of major limb vessels.