the most caudal subdivision of the brainstem, immediately continuous with the spinal cord, extending from the lower border of the decussation of the pyramid to the pons; its anterior (ventral) surface resembles that of the spinal cord except for the bilateral prominence of the inferior olive; the posterior (dorsal) surface of its upper half forms part of the floor of the fourth ventricle. Motor nuclei of the medulla oblongata include the hypoglossal nucleus, the dorsal motor nucleus, inferior salivatory nucleus, and the nucleus ambiguus; sensory nuclei include the nuclei of the posterior column (gracile and cuneate), the cochlear and vestibular nuclei, the middle and caudal portions of the spinal trigeminal nucleus, and the nucleus of the solitary tract.
Synonym(s): myelencephalonTA, oblongata
See Also: medulla
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