Adjacent Words

medulla definitions

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WordNet (r) 3.0 (2005)

n
1: a white fatty substance that forms a medullary sheath around the axis cylinder of some nerve fibers [syn: myelin, myeline, medulla]
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" [syn: medulla oblongata, medulla, bulb]
3: the inner part of an organ or structure in plant or animal [ant: cortex]

Merriam Webster's

noun (plural -las or medullae) Etymology: Middle English, from Latin Date: 15th century 1. plural medullae a. bone marrow b. medulla oblongata 2. a. the inner or deep part of an animal or plant structure <the adrenal medulla> b. myelin sheath

Oxford Reference Dictionary

n. 1 the inner region of certain organs or tissues usu. when it is distinguishable from the outer region or cortex, as in hair or a kidney. 2 the myelin layer of certain nerve fibres. 3 the soft internal tissue of plants. Phrases and idioms: medulla oblongata the continuation of the spinal cord within the skull, forming the lowest part of the brain stem. Derivatives: medullary adj. Etymology: L, = pith, marrow, prob. rel. to medius middle

Webster's 1913 Dictionary

Medulla Me*dul"la, n. [L.] 1. Marrow; pith; hence, essence. [Obs.] --Milton. 2. (Anat.) The marrow of bones; the deep or inner portion of an organ or part; as, the medulla, or medullary substance, of the kidney; specifically, the medula oblongata. 3. (Bot.) A soft tissue, occupying the center of the stem or branch of a plant; pith. Medulla oblongata. [L., oblong medulla] (Anat.), the posterior part of the brain connected with the spinal cord. It includes all the hindbrain except the cerebellum and pons, and from it a large part of the cranial nerves arise. It controls very largely respiration, circulation, swallowing, and other functions, and is the most vital part of the brain; -- called also bulb of the spinal cord. See Brain.