Sphingomyelin is a major lipid component of the myelin sheath, which insulates nerve fibers and enhances rapid nerve impulse conduction. It is abundant in the membranes of myelinating cells such as Schwann cells and oligodendrocytes. Unlike triglycerides, which are energy storage lipids, sphingomyelin contributes structurally and functionally to the compact, multilamellar myelin sheath. Cholesterol is also present but sphingomyelin is more specific to myelin. Phosphatidylcholine is common in cell membranes but less specific to myelin sheaths. Understanding this is crucial in diagnosing and managing demyelinating diseases like multiple sclerosis.

Reference: Gray’s Anatomy, Standring S, 42nd Edition.