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Related to white matter: gray matter
1. physical material having form and weight under ordinary conditions; called also substance.
gray matter areas of the nervous system where the nerve fibers are unmyelinated (not enveloped by a myelin sheath); it contains the bodies of the nerve cells. Tissue composed of myelinated fibers is called white matter. The cerebral cortex is entirely composed of gray matter and the cerebellum also contains some deep-seated masses of it. The spinal cord has a central core of gray matter surrounded by white matter; in cross section, its gray matter is shaped approximately like the letter H. Called also substantia grisea and gray substance.
those regions of the brain and spinal cord that are largely or entirely composed of nerve fibers and contain few or no neuronal cell bodies or dendrites.
Whitish nerve tissue, especially of the brain and spinal cord, consisting chiefly of myelinated nerve fibers.
the tissue of the central nervous system and much of the part of the cerebrum, consisting mainly of myelinated nerve fibers, but with some unmyelinated nerve fibers, embedded in a spongy network of neuroglia. It is subdivided in each half of the spinal cord into three funiculi: the anterior, the posterior, and the lateral white column. Each column subdivides into tracts that are closely associated in function. The anterior column divides into two ascending tracts and five descending tracts. The posterior column divides into two large ascending tracts, one small descending tract, and one intersegmental tract. The lateral column divides into six ascending tracts and four descending tracts. Also called white substance. Compare gray matter. See also cerebrum, spinal cord, spinal tract.
white mat·ter(wīt mat'ĕr) [TA]
white matterThose parts of the central nervous system that appear white on section because they consist mainly of myelinated nerve fibres. Compare grey matter which consists mainly of nerve cell bodies.
white matterthe tissue of the CENTRAL NERVOUS SYSTEM, lying outside the GREY MATTER in the spinal cord but internal to grey matter in the brain of some vertebrates, and which contains the myelinated AXONS of nerves. The MYELIN SHEATHS give the tissue its white appearance.
white matter, white substance
the white nervous tissue, constituting the conducting portion of the brain and spinal cord, composed mostly of myelinated nerve fibers. Gray matter or substance is the term used to describe the tissues composed of unmyelinated fibers.