medulla meaning and definition

MEDULLA noun

Definition of medulla (noun)

1. a white fatty substance that forms a medullary sheath around the axis cylinder of some nerve fibers
   • synonyms: myelin, myeline
2. 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"
   • synonyms: bulb, medulla oblongata
3. the inner part of an organ or structure in plant or animal
   • antonym: cortex