Practice question

Salamander limb regeneration occurs through epimorphosis characterized by histolysis, dedifferentiation, formation of regeneration blastema, extensive proliferation, and re-differentiation recapitulating developmental programs. After amputation wound epidermis forms apical epidermal cap expressing FGF8, Wnt, BMP modulators, nerves provide trophic factors inducing MMP degradation and cell-cycle re-entry. Blastema accumulates multipotent progenitors restoring missing portion distal to cut. This contrasts morphallaxis where existing tissues repattern without growth, compensatory hypertrophy, or simple stem-cell renewal. Molecularly re-activation of FGF10-FGF8, SHH-Gremlin loops indicates redeployment of limb development pathways during epimorphic regeneration.