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Degeneration is the first stage of nerve repair. The wound fills with haematoma and Schwann cells divide locally. Fibroblasts migrate in and deposit collagen. Cell bodies of injured axons begin to swell and there is evidence of new protein production for repair. The part of the axon distal to the level of the injury breaks down by a process termed Wallerian degeneration. The distal axon degrades for the first two days after injury. Local Schwann cells govern the phagocytic degradation of the axon and the clearance of the surrounding myelin sheath for up to 14 days. This process can extend proximally down the nerve for up to 2cm from the point of injury to a node of Ranvier. Laterly, the perineurium breaks down.
With no neural impulses, synapses distal to the nerve injury break up and consequently, the end organ itself may atrophy.