medˈullated adjective

Provided with a medullary sheath

medulla oblongāˈta (or /-äˈtə/) noun

That part of the brain that tapers off into the spinal cord

medullary ray noun (botany)

A band of cells (appearing as a ray in cross-section) cutting radially through wood and bast

medullary sheath noun

1. A thin layer surrounding the pith (botany)
2. A whitish fatty membrane which surrounds the axons of the central nervous system in vertebrates and acts as an insulating coat (anatomy)