- The fatty substance that covers and protects nerves. Myelin is a layered tissue surrounding the axons or nerve fibers. The sheath around the nerve fibers which acts electrically as a conduit in an electrical system, ensuring that messages sent by nerve fibers are not lost en route.
* * *1. The lipoproteinaceous material, composed of regularly alternating membranes of lipid lamellae (cholesterol, phospholipids, sphingolipids, phosphatidates) and protein, of the m. sheath. 2. Droplets of lipid formed during autolysis and postmortem decomposition.
* * *my·e·lin 'mī-ə-lən n a soft white somewhat fatty material that forms a thick myelin sheath about the protoplasmic core of a myelinated nerve fibermy·e·lin·ic .mī-ə-'lin-ik adj
* * *n.a complex material formed of protein and phospholipid that is laid down as a sheath around the axon of certain neurones, known as myelinated (or medullated) nerve fibres. The material is produced and laid down in concentric layers by Schwann cells at regular intervals along the nerve fibre. Myelinated nerves conduct impulses more rapidly than nonmyelinated nerves.
* * *my·elin (miґə-lin) [Gr. myelos marrow] the substance of the cell membrane of Schwann cells that coils to form the myelin sheath (see under sheath); it has a high proportion of lipid to protein and serves as an electrical insulator. myelinic adj
Medical dictionary. 2011.