THORAX ABDOMEN AND PELVIS

Detailed explanation-1: -The myelin sheath is a greatly extended and modified plasma membrane wrapped around the nerve axon in a spiral fashion [1]. The myelin membranes originate from and are a part of the Schwann cells in the peripheral nervous system (PNS) and the oligodendroglial cells in the central nervous system (CNS) (see Chap. 1).

Detailed explanation-2: -In the PNS, axons carry signals to muscles and glands or from sensory organs such as the skin. Each myelin sheath is formed by the concentric wrapping of an oligodendrocyte (CNS) or Schwann cell (PNS) process (a limb-like extension from the cell body) around the axon.

Detailed explanation-3: -Myelinating Schwann cells wrap a single axon, while a CNS oligodendrocyte may wrap several axons. Nonmyelinating Schwann cells may surround areas of several unmyelinated axons. A series of Schwann cells encloses an axon along its entire length.