#medullary_sheath__medullarysheath__myelin_sheath  a layer of myelin encasing (and insulating) the axons of medullated nerve fibers
  supertype:  sheath.natural_covering__case  an enveloping structure or covering enclosing an animal or plant organ or part
  part:  axolemma  Ranvier's_nodes  oligodendroglia
  substance:  myelin
  part of:  medullated_nerve_fiber__myelinated_nerve_fiber  a nerve fiber encased in a sheath of myelin

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