Definition: The lipid-rich sheath surrounding AXONS in both the central and peripheral nervous systems. The myelin sheath is an electrical insulator and allows faster and more energetically efficient conduction of impulses. The sheath is formed by the cell membranes of glial cells (SCHWANN CELLS in the peripheral and OLIGODENDROGLIA in the central nervous system). Deterioration of the sheath in DEMYELINATING DISEASES is a serious clinical problem.
X ref MYELIN is the substance of the myelin sheath: do not confuse with MYELIN BASIC PROTEINS; myelination: index under MYELIN SHEATH /physiol
Other names Myelin; Sheaths, Myelin; Sheath, Myelin; Myelin Sheaths