medullary sheath Hear it!

medullary sheath definition

medullary sheath

  1. Anat. a layer of myelin forming a sheath around certain nerve fibers
  2. Bot. a ring of primary xylem around the pith of some stems

Webster's New World College Dictionary Copyright © 2009 by Wiley Publishing, Inc., Cleveland, Ohio.
Used by arrangement with John Wiley & Sons, Inc.

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