Structure and/or Key Features
In the central nervous system, the myelin sheath consists of extensions of the plasmalemma of the oligodendrocyte forming concentric layers (or lamellae) around neighboring axons. The myelin sheath can thicken from a just few lamellae to about 200 lamellae (Standring, 2016).
Related parts of the anatomy
References
Standring, S. (2016) Gray's Anatomy: The Anatomical Basis of Clinical Practice. Gray's Anatomy Series 41 edn.: Elsevier Limited.