The cell bodies of motor neurons in the peripheral nerve are found within the CNS in regions termed ' nuclei ' or outside the CNS in ' ganglia '. The cell odies of sensory neurons are located outside the CNS in ganglia. Longitudinal sections of small peripheral nerves will demonstrate a wavy appearance. The nuclei of the Schwann cells also exhibit this 'waviness'. While the bulk of the peripheral 'nerve' consists of nerve fibers and their supporting Schwann cells, the nerve fibers are surrounded by a consecutive series of connective tissue sheaths which provides resilience and protection to the nerve.
Blood vessels penetrate it to supply blood to the nerve fibers and surrounding tissue.
It may be absent in small nerves. Perineurium Bundles of nerve fibers with their thin connective tissue sheaths are bound into fascicles by another sheath. This sheath may be several concentric cell layers thick and is characterized by squamous cells demonstrating a basal lamina. Microfilaments are present in these squamous cells and demonstrate a contractile abiltiy. Although collagen fibrils may be present between the cellular layers, typical fibroblasts are absent in the perineurium.