| AO | abdominal aorta; achievement orientation; acid output; acridine orange; ankle orthosis; anodal openi... |
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| AOS | American Ophthalmological Society; American Otological Society; anodal opening sound; anterior [o]es... |
| AP | accessory pathway; accounts payable; acid phosphatase; acinar parenchyma; action potential; active p... |
| A&P | anterior and posterior; assessment and plans; auscultation and percussion |
| APA | action potential amplitude; aldosterone-producing adenoma; Ambulatory Pediatric Association; America... |
| anterior medullary velum | The thin layer of white matter stretching between the two superior cerebellar peduncles, forming the roof of the superior recess of the fourth ventricle. Synonym: velum medullare superius, anterior medullary velum, Vieussens' valve. (05 Mar 2000) |
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| anterior megalophthalmos | Congenital anomaly consisting of an enlarged anterior segment of the eye. Synonym: anterior megalophthalmos, megalocornea. Origin: kerato-+ L. Globus, ball (05 Mar 2000) |
| anterior meningeal artery | <anatomy, artery> Origin, anterior ethmoidal; distribution, meninges in anterior cranial fossa; anastomoses, branches of middle meningeal and meningeal branches of internal carotid and lacrimal. Synonym: arteria meningea anterior. (05 Mar 2000) |
| anterior meniscofemoral ligament | <anatomy> The ligamentous band that passes anterior to the posterior cruciate ligament, extending between the posterior portion of the lateral meniscus and the upper end of the anterior cruciate ligament. Synonym: ligamentum meniscofemorale anterius, Humphry's ligament. (05 Mar 2000) |
| anterior myocardial infarction | Infarction involving the anterior wall of the heart, and producing indicative electrocardiographic changes in the anterior chest leads and often in limb lead I. (05 Mar 2000) |
| anterior naris | 1. <anatomy> One of the external openings of the nose, which give passage to the air breathed and to secretions from the nose and eyes; one of the anterior nares. In sperm whales, porpoises, and allied animals, there is only one nostril, which is situated on the top of the head and called a spiracle. 2. Perception; insight; acuteness. "Methinks a man Of your sagacity and clear nostril should Have made another choice." (B. Jonson) Origin: OE. Nosethril, nosethirl, AS. Nospyrl; nos for nosu nose + pyrel opening, hole, from pyrel pierced, for pyrhel, fr. Purh through. See Nose, and Through, and cf. Thrill. Source: Websters Dictionary (01 Mar 1998) |
| anterior nasal aperture | The anterior nasal opening in the skull. Synonym: apertura piriformis, piriform opening. (05 Mar 2000) |
| anterior nasal spine | A pointed projection at the anterior extremity of the intermaxillary suture; the tip, as seen on a lateral cephalometric radiograph, is used as a cephalometric landmark. Synonym: spina nasalis anterior. (05 Mar 2000) |
| anterior neuropore | The temporary opening at the extreme rostral (cephalic) end of the early embryonic forebrain; closes at the 20th somite stage. Synonym: anterior neuropore, cranial neuropore. (05 Mar 2000) |
| anterior notch of cerebellum | A wide, shallow notch on the anterior surface of the cerebellum occupied laterally by the superior cerebellar peduncles and the inferior quadrigeminal bodies medially. Synonym: anterior notch of cerebellum, incisura cerebelli anterior, semilunar notch. (05 Mar 2000) |
| anterior notch of ear | A notch between the supratragic tubercle and the crus of the helix. Synonym: incisura anterior auris, anterior auricular groove, auricular notch, sulcus auriculae anterior. (05 Mar 2000) |
| anterior nuclei of thalamus | Collective term for three groups of nerve cells which together form the anterior thalamic tubercle: the anteroventral nuclei, a relatively large nucleus; the anteromedial nuclei; and the anterodorsal nuclei, a small (but large-celled) nucleus. The nuclei receive the mamillothalamic tract from the mamillary body, and additional afferents by way of the fornix; they project collectively to the cortex of the cingulate and parahippocampal gyrus. Synonym: nuclei anteriores thalami. (05 Mar 2000) |
| anterior occlusion | The occlusion of anterior teeth. Synonym: mesial occlusion. (05 Mar 2000) |
| anterior ocular segment | That portion of the eye comprising the cornea, iris, lens, and their associated chambers and adnexa. (05 Mar 2000) |
| anterior palatine arch | One of a pair of ridges or folds of mucous membrane passing from the soft palate to the side of the tongue; it encloses the palatoglossus muscle and forms anterior margin of the tonsillar fossa. Also demarcates oral cavity from isthmus of fauces. Synonym: arcus palatoglossus, anterior palatine arch, anterior pillar of fauces, arcus glossopalatinus, glossopalatine arch, glossopalatine fold. (05 Mar 2000) |