Also found in: Thesaurus, Medical, Legal, Encyclopedia, Wikipedia.
See myelin sheath.
1. (Anatomy) anatomy a myelin layer surrounding and insulating certain nerve fibres
2. (Botany) a layer of thick-walled cells surrounding the pith of the stems of some higher plants
1. a narrow zone made up of the innermost layer of woody tissue immediately surrounding the pith in plants.
Switch to new thesaurus
|Noun||1.||medullary sheath - a layer of myelin encasing (and insulating) the axons of medullated nerve fibers|
axolemma - outer membrane covering an axon
oligodendria, oligodendroglia - tissue consisting of glial cells with sheetlike processes that form the myelin sheath of nerve fibers