| MNA | maximum noise area |
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| MPA | mean pulmonary arterial [pressure]; medial preoptic area; Medical Procurement Agency; medroxyprogest... |
| MPOA | medial preoptic area |
| MSA | major serologic antigen; male-specific antigen; mannitol salt agar; Medical Services Administration;... |
| MTAC | mass transfer area coefficient |
| anterior descending artery | <anatomy, artery> Anterior interventricular branch of left coronary artery. Terminal branch (with circumflex coronary artery) of left coronary artery; descends in anterior interventricular groove to apex, anastomosing with posterior interventricular artery. Supplies most of sternal aspect of ventricles and anterior two-thirds of interventricular septum, including atrioventricular bundle of conducting tissue. Synonym: ramus interventricularis anterior arteriae coronariae sinistrae, anterior descending artery. (05 Mar 2000) |
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| anterior drawer test | <investigation> This test is performed with the patient lying on their back with there knee in 90 degrees of flexion with the foot resting firmly on the table. The examiner grasps the top portion of the shin with both hands, positioning the thumbs on either tibial condyle. Stabilising the foot the examiner places pressure slowly on the proximal tibia by moving the shin toward the examiner. Abnormal looseness and movement forward indicates a significant anterior cruciate ligament injury. (27 Sep 1997) |
| anterior elastic layer | A transparent homogeneous acellular layer, 6 to 9 um thick, lying between the basal lamina of the outer layer of stratified epithelium and the substantia propria of the cornea; considered to be a basement membrane. Synonym: lamina limitans anterior corneae, anterior elastic layer, Bowman's membrane, lamina elastica anterior, limiting layers of cornea. (05 Mar 2000) |
| anterior embryotoxon | An opaque, grayish ring at the periphery of the cornea just within the sclerocorneal junction, of frequent occurrence in the aged; it results from a deposit of fatty granules in, or hyaline degeneration of, the lamellae and cells of the cornea. Synonym: anterior embryotoxon, arcus adiposus, arcus juvenilis, arcus lipoides, arcus senilis, gerontoxon, linea corneae senilis, lipoidosis corneae. (05 Mar 2000) |
| anterior epithelium of cornea | The stratified squamous epithelium covering the outer surface of the cornea; it is smooth, consists usually of five layers of cells, and contains numerous free nerve endings. Synonym: epithelium anterius corneae. (05 Mar 2000) |
| anterior ethmoidal air cells | The anterior group of air cells of the ethmoidal sinus's; each sinus communicates with the middle meatus of the nasal cavity. Synonym: sinus ethmoidales anteriores, anterior cells, anterior sinuses, cellulae anteriores. (05 Mar 2000) |
| anterior ethmoidal artery | <anatomy, artery> Origin, ophthalmic; distribution, cerebral membranes in anterior cranial fossa, anterior ethmoidal cells, frontal sinus, anterior upper part of nasal mucous membrane, skin of dorsum of nose. Synonym: arteria ethmoidalis anterior. (05 Mar 2000) |
| anterior ethmoidal nerve | <anatomy, nerve> A branch of the nasociliary nerve; passes through anterior ethmoidal foramen on superomedial wall of orbit into cranial cavity, giving rise to anterior meningeal nerves, then passes through cribriform plates into nasal cavity, supplying anterosuperior nasal mucosa. Synonym: nervus ethmoidalis anterior. (05 Mar 2000) |
| anterior extremity | Specifically, the anterior end of the spleen (extremitas anterior splenis ). Synonym: extremitas anterior. (05 Mar 2000) |
| anterior extremity of caudate nucleus | The head or anterior extremity of the caudate nucleus projecting into the anterior horn of the lateral ventricle. Synonym: caput nuclei caudati, anterior extremity of caudate nucleus. (05 Mar 2000) |
| anterior eye segment | That part of the eyeball anterior to the lens. (12 Dec 1998) |
| anterior facial vein | <anatomy, vein> A continuation of the angular vein at the medial angle of the eye. It passes diagonally downward and outward, joining with the retromandibular vein below the border of the lower jaw before emptying into the internal jugular vein. Synonym: anterior facial vein, vena facialis anterior, vena facialis. (05 Mar 2000) |
| anterior femoral cutaneous nerves | Anterior cutaneous branches of femoral nerve; supplies distal 3/4 of skin and superficial fascia of anterior and medial thigh. Synonym: rami cutanei anteriores nervi femoralis. (05 Mar 2000) |
| anterior focal point | The point where parallel rays from the retina are focused. (05 Mar 2000) |
| anterior fontanel | A diamond-shaped membranous interval at the junction of the coronal, sagittal, and metopic sutures where the frontal angles of the parietal bones meet the two ununited halves of the frontal bone. Synonym: fonticulus anterior, bregmatic fontanel, frontal fontanel. (05 Mar 2000) |