Abstract

ULTRATRSUCTURAL CHANGES OF SCHWANN CELLS DURING NERVE REGENERATION FOLLOWING CRUSH INJURY OF THE SURAL NERVE IN RATS.

By

Abdulmonem. Alhayani

Anatomy Department, Faculty of Medicine, King’s Abdullaziz University. KSA

          Twenty-four albino male rats weighted between 200 g to 250 g were used in the present study. The left sural nerves of 18 rats were subjected to crush injury while the sural nerves of 6 animals were used as control. Schwann cells after one week of the crush injury showed multiple cytoplasmic processes. Those with long cytoplasmic processes wrapped only one axon while those wrapping multiple unmyelinated nerve axons showed shorter processes. Some of these processes wrapped or surrounded collagen bundles “collagen pockets” and degenerated myelin. Some of these processes contained electronlucent vacuoles. Schwann cell cytoplasm showed asymmetric hypertrophy and contained excessive amounts of rough endoplasmic reticulum and ribosomes. Also electronlucent vacuoles and electrondense bodies of the degenerated myelin whorls were encountered in the cytoplasm of some Schwann cells. Schwann cells were surrounded by basal laminae which may be redundant. After second week of the crush injury. The number of the regenerating Schwann cells were increased in number and the myelin sheaths covering the myelinated nerve axons were more thicker. Schwann cells were possessing long cytoplasmic processes that wrapped unmyelinated nerve axons. After third week of the crush injury, Schwann cells wrapped compressed myelinated nerve axons with degeneration of the myelin of such axons. The number of the myelinated nerve axons were increased and the thickness of the myelin sheath were also increased. It could be concluded that Schwann cells have phagocytic role of during regeneration of the peripheral nerves that was indicated by the presence of cytoplasmic electronlucent vacuoles and electron dense whorls of degenerated myelin. Such phagocytic process might be performed by the use of their cytoplasmic processes.