In Wallerian degeneration following peripheral nerve injury, the distal axon and its myelin sheath undergo degeneration. Which cells phagocytose the myelin debris and are essential for subsequent nerve regeneration?

• A Microglia
• B Astrocytes
• C Oligodendrocytes
• D Schwann cells and macrophages ✓

Explanation

In Wallerian degeneration, Schwann cells dedifferentiate and, along with macrophages, phagocytose the distal axon and myelin debris. The Schwann cells then form tubular structures called Bands of Büngner, which guide regenerating axonal sprouts from the proximal stump distally. Schwann cells also secrete neurotrophic factors (NGF, BDNF, CNTF) supporting axonal regrowth at ~1 mm/day. Microglia are CNS phagocytes; oligodendrocytes myelinate CNS axons and do not support peripheral nerve regeneration.

Reference: BD Chaurasia's Human Anatomy, 8th ed.

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Written and medically reviewed by the StethoPrep medical team.