Related Definitions
[n] the inner part of an organ or structure in plant or animal
[n] lower or hindmost part of the brain; continuous with spinal cord; (`bulb' is an old term for medulla oblongata); "the medulla oblongata is the most vital part of the brain because it contains centers controlling breathing and heart functioning"
[n] a white fatty substance that forms a medullary sheath around the axis cylinder of some nerve fibers