| MSA | major serologic antigen; male-specific antigen; mannitol salt agar; Medical Services Administration;... |
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| MTAC | mass transfer area coefficient |
| MVA | mechanical ventricular assistance; mevalonic acid; mitral valve area; motor vehicle accident |
| MVOA | mitral valve orifice area |
| NCA | National Certification Agency; National Council on Aging; National Council on Alcoholism; neurocircu... |
| anterior cervical intertransverse muscles | Origin, anterior tubercle of cervical transverse process; insertion, anterior tubercle of next superior transverse process; action, abducts cervical vertebrae; nerve supply, ventral branch of cervical nerves. Synonym: musculi intertransversarii anteriores cervicis, anterior cervical intertransverse muscles. (05 Mar 2000) |
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| anterior cervical lymph nodes | The group of lymph nodes located in the anterior region of the neck, divided into superficial and deep groups. Synonym: nodi lymphatici cervicales anteriores. (05 Mar 2000) |
| anterior chamber | The space in the eye, filled with aqueous humor, bounded anteriorly by the cornea and a small portion of the sclera and posteriorly by a small portion of the ciliary body, the iris, and that part of the crystalline lens which presents through the pupil. (12 Dec 1998) |
| anterior chamber cleavage syndrome | <syndrome> A congenital disorder originating from faulty separation of embryonic structures; it results in bilateral central corneal opacities, with an anterior ring attachment of the iridic pupillary border and anterior polar cataracts; associated with short-limbed dwarfism; autosomal dominant inheritance. See: iridocorneal endothelial syndrome. Synonym: Peters' anomaly. (05 Mar 2000) |
| anterior chamber of eye | The space between the cornea anteriorly and the iris/pupil posteriorly, filled with a watery fluid (aqueous humor) and communicating through the pupil with the posterior chamber. Synonym: camera anterior bulbi, camera oculi anterior, camera oculi major. (05 Mar 2000) |
| anterior chamber trabecula | Tissue at the angle of the anterior chamber through which aqueous humor exits from the eye. (05 Mar 2000) |
| anterior choroidal artery | <anatomy, artery> Origin, internal carotid or (rarely) middle cerebral artery; distribution, optic tract, crus cerebri, uncus, hippocampus, globus pallidus, posterior part of internal capsule, geniculate bodies of the thalamus, and choroid plexus in the inferior horn of the lateral ventricle. Synonym: arteria choroidea anterior. (05 Mar 2000) |
| anterior choroiditis | Disseminated choroiditis restricted to peripheral choroid. (05 Mar 2000) |
| anterior ciliary artery | <anatomy, artery> One of several arteries derived from muscular branches of the ophthalmic which perforate the anterior part of the sclera and anastomose with posterior ciliary arteries. Synonym: arteria ciliaris anterior. (05 Mar 2000) |
| anterior circumflex humeral artery | <anatomy, artery> Origin, axillary; distribution, shoulder joint and biceps muscle; anastomoses, posterior circumflex humeral artery. Synonym: arteria circumflexa humeri anterior, anterior humeral circumflex artery. (05 Mar 2000) |
| anterior clear space | On lateral chest radiographs, the region dorsal to the sternum and ventral to the ascending aorta. Synonym: anterior clear space. (05 Mar 2000) |
| anterior column | The pronounced, ventrally oriented ridge of gray matter in each half of the spinal cord; it corresponds to the anterior or ventral horn appearing in transverse sections of the cord, and contains the motor neurons innervating the skeletal musculature of the trunk, neck, and extremities. See: gray columns. Synonym: columna anterior. (05 Mar 2000) |
| anterior column of medulla oblongata | An elongated, white prominence on the ventral surface of the medulla oblongata on either side along the anterior median fissure, corresponding to the pyramidal tract. Synonym: pyramis medullae oblongatae, anterior column of medulla oblongata, anterior pyramid. (05 Mar 2000) |
| anterior commissure | A round bundle of nerve fibres that crosses the midline of the brain near the anterior limit of the third ventricle. It consists of a smaller anterior part, the fibres of which pass in part to the olfactory bulbs, and a larger posterior part, which interconnects the left and right temporal lobes. Synonym: commissura anterior. (05 Mar 2000) |
| anterior communicating artery | <anatomy, artery> A short vessel joining the two anterior cerebral arteries and completing the cerebral arterial circle (circle of Willis) anteriorly. Synonym: arteria communicans anterior. (05 Mar 2000) |