medullary sheath

noun

1. Botany.,  a narrow zone made up of the innermost layer of woody tissue immediately surrounding the pith in plants.

2. Anatomy.,  myelin sheath.

medullary sheath

noun

1. anatomy a myelin layer surrounding and insulating certain nerve fibres

2. a layer of thick-walled cells surrounding the pith of the stems of some higher plants

Word History and Origins

Origin of medullary sheath¹

First recorded in 1840–50