Wallerian Degeneration

Wallerian Degeneration

Question 1. What is peripheral nerve? List its connective tissue sheaths.
Answer.

The peripheral nerve is a bundle of nerve fibers outside the central nervous system. Examples of peripheral nerves are 12 pairs of cranial nerves and 31 pairs of spinal nerves.

Connective tissue sheaths of peripheral nerve They are three in number as follows:

• • Endoneurium, which encloses a single nerve fiber.
  • Perineurium, which encloses a bundle (group) of nerve fibers.
  • Epineurium, which encloses the entire nerve

Question 2. Write a short on Wallerian degeneration.
Answer.

When the peripheral nerve is injured, it undergoes a process of degeneration. The changes in the part of the axon, distal to the injury are referred to as Wallerian (anterograde) degeneration. When the myelinated nerve fiber is cut, the distal segment of the cut nerve fiber gets completely fragmented and lost.

Its sheath also degenerates; however, myelin-producing sheath cells (astrocytes) survive. The Schwann cells proliferate, enlarge in size, and form solid cellular cords within the sheath of the endoneurium. Now, the proximal segment of the nerve fiber grows into the endoneural tube.