Fig. 5. Degeneration and regeneration after peripheral nerve injury. (A) Normal neuron and nerve fiber. (B) Wallerian degeneration. The axotomy results in fragmentation of the distal axon and myelin sheaths. Schwann cells proliferate. Macrophages invade the distal nerve segment, and phagocytize degrading materials. (C) Schwann cells in the distal segment line up in bands of Büngner. Axonal sprouts advance embedded in the Schwann cells and are attracted by gradients of neurotrophic factors. (D) Axonal reconnection with end organs and maturation and remyelination of the nerve fiber [22].
