#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
  substance:  myelin
  part of:  medullated_nerve_fiber
  part:  axolemma  outer membrane covering an axon
  part:  Ranvier's_nodes__nodes_of_Ranvier  small gaps in the myelin sheath of medullated axons
  part:  oligodendroglia  tissue consisting of glial cells with sheet-like processes that form the myelin sheath of nerve fibers
     part:  oligodendrocyte  a cell of the oligodendroglia

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