- Medulla
- The innermost part. The spinal medulla, for example, is that part of the spinal cord that is lodged within the vertebral canal.
* * *Any soft marrow-like structure, especially in the center of a part. SEE ALSO: m. oblongata. SYN: substantia medullaris (1). [L. marrow, fr. medius, middle]- m. of hair shaft the central axis of some hairs, containing a column of large vacuolated and keratinized cells; the medullary portion is surrounded by the cortex.- m. of lymph node [TA] the central portion of a node consisting of cordlike masses of lymphocytes, plasma cells, and macrophages in a stroma of reticular fibers separated by lymph sinuses; it reaches the surface of the node at the hilum. SYN: m. nodi lymphoidei [TA].- m. oblongata [TA] 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 ventral surface resembles that of the spinal cord except for the bilateral prominence of the inferior olive; the dorsal surface of its upper half forms part of the floor of the fourth ventricle. Motor nuclei of the m. 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 mid and caudal portions of the spinal trigeminal nucleus, and the nucleus of the solitary tract. SEE ALSO: m.. SYN: myelencephalon [TA], oblongata.- m. ossium [TA] SYN: bone marrow.- renal m. [TA] the inner, darker portion of the kidney parenchyma consisting of the renal pyramids. SYN: m. renalis [TA], m. of kidney.- m. renalis [TA] SYN: renal m..- m. of suprarenal gland [TA] it is composed principally of anastomosing cords of cells in the core of the gland; the cells display a chromaffin reaction because of the presence of epinephrine and norepinephrine in their granules. SYN: m. glandulae suprarenalis [TA], m. of adrenal gland, suprarenal m..
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1) pl medullaea) BONE MARROWb) MEDULLA OBLONGATA2 a) the inner or deep part of an organ or structure <the adrenal \medulla>b) MYELIN SHEATH* * *
n.1. the inner region of any organ or tissue when it is distinguishable from the outer region (the cortex), particularly the inner part of the kidney, adrenal glands, or lymph nodes.3. the myelin layer of certain nerve fibres.• medullary adj.* * *
me·dul·la (mə-dulґə) gen. and pl. medulґlae [L.] 1. the most interior portion of an organ or structure. 2. m. oblongata. 3. m. ossium.
Medical dictionary. 2011.
