Figure 5.

Key tissue components of regenerating nerves. (a) Regeneration unit, and (b) fibroblasts and immune cells providing essential signals to the Schwann cells of the regeneration units. In the distal stump, denervated Schwann cells convert to a repair supportive phenotype. These repair (Bungner) Schwann cells form regeneration tracks (Bungner bands; dark blue cells) that guide regenerating axons back to their targets and provide essential trophic support for injured neurons. After crush injury, axons are severed but the Schwann cell basal lamina tubes and connective sheaths remain continuous between the proximal and distal stump. This allows axons to reach the distal stump within their original basal lamina tubes. After nerve cut, the length of the bridge depends on the extent of the injury and the nature of any subsequent surgical intervention.