myelin

American  

[mahy-uh-lin] / ˈmaɪ ə lɪn /

Also myeline

noun

Biology.

1. a soft, white, fatty material in the membrane of Schwann cells and certain neuroglial cells: the substance of the myelin sheath.

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myelin British  

/ ˈmaɪɪˌliːn, ˈmaɪɪlɪn /

noun

1. a white tissue forming an insulating sheath ( myelin sheath ) around certain nerve fibres. Damage to the myelin sheath causes neurological disease, as in multiple sclerosis

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myelin Scientific  

/ mī′ə-lĭn /

1. A whitish, fatty substance that forms a sheath around many vertebrate nerve fibers. Myelin insulates the nerves and permits the rapid transmission of nerve impulses. The white matter of the brain is composed of nerve fibers covered in myelin.

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Other Word Forms

• myelinic adjective

Etymology

Origin of myelin

First recorded in 1865–70; myel- + -in ²

Example Sentences

To test this idea, Zhang and his team examined whether the mutation could protect the myelin sheath.

From Science Daily • Apr. 15, 2026

The affected areas also contained greater numbers of mature oligodendrocytes, the cells responsible for producing myelin.

From Science Daily • Apr. 15, 2026

Multiple sclerosis occurs when the immune system mistakenly attacks myelin, the protective layer surrounding nerve fibers in the brain and spinal cord.

From Science Daily • Feb. 6, 2026

Demyelination is the process in which the myelin sheath -- a protective, insulating layer surrounding nerve fibers in the brain and spinal cord -- is damaged or destroyed.

From Science Daily • Jan. 6, 2026

Throughout adolescence, the brain is busily lining important neural pathways with a fatty sheath called myelin.

From "The 57 Bus" by Dashka Slater