| AS | acetylstrophanthidin; acidified serum; acoustic schwannoma; acoustic stimulation; active sarcoidosis... |
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| AVA | activity vector analysis; antiviral antibody; aortic valve area; aortic valve atresia; arteriovenous... |
| AVO | aortic valve opening; aortic valve orifice; atrioventricular opening |
| SAR | scatter/air ratio; seasonal allergic rhinitis; sexual attitude reassessment; slowly adapting recepto... |
| SVAS | supravalvular aortic stenosis; supraventricular aortic stenosis |
| nail bed | The area of the corium on which the nail rests; it is extremely sensitive and presents numerous longitudinal ridges on its surface. According to some anatomists, the nail bed is the portion covered by the body of the nail, the nail matrix being only the part on which the root of the nail rests. Synonym: matrix unguis, keratogenous membrane, nail matrix, onychostroma. (05 Mar 2000) |
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| fluidised-bed boiler | A large, refractory-lined vessel with an air distribution member or plate in the bottom, a hot gas outlet in or near the top, and some provisions for introducing fuel. The fluidised bed is formed by blowing air up through a layer of inert particles (such as sand or limestone) at a rate that causes the particles to go into suspension and continuous motion. The super-hot bed material increased combustion efficiency by its direct dontact with the fuel. (05 Dec 1998) |
| fracture bed | A narrow, extra-firm bed for treatment of fractures; usually incorporates an overhead frame for traction apparatus. (05 Mar 2000) |
| abdominal aortic aneurysm | <surgery> A distended and weakened area in the wall of the abdominal aorta, more common in those who suffer from atherosclerosis. Symptoms include sudden, severe abdominal pain with radiation to the back. (27 Sep 1997) |
| abdominal aortic coarctation | <radiology> 2% of all coarctations, (most common site is thoracic: just distal to origin of L SCA), may be isolated congenital anomaly, associated with: thoracic aortic coarctation, idiopathic hypercalcaemia syndrome, rubella syndrome (ToRCHS), Takayasu arteritis, neurofibromatosis, radiation therapy, fibromuscular disease (12 Dec 1998) |
| abdominal aortic plexus | <anatomy, neurology> An autonomic plexus surrounding the abdominal aorta, directly continuous with the thoracic aortic plexus above and continued inferior to the bifurcation of the aorta as the superior hypogastric plexus. Synonym: plexus aorticus abdominalis. (05 Mar 2000) |
| acute aortic dissection | <cardiology> A condition in which a weakened portion of the thoracic aorta begins to tear along the longitudinal axis of the vessel. Symptoms include sudden, severe chest pain that may radiate to the back accompanied by nausea, sweating and difficulty breathing. A common risk factor for this event is atherosclerotic vascular disease and-or hypertension. Advanced cases of syphilis (syphilitic aortitis) can also result in acute thoracic dissection as a complication of infection with Treponema pallidum. (27 Sep 1997) |
| aortic | Relating to the aorta or the aortic orifice of the left ventricle of the heart. Synonym: aortal. (05 Mar 2000) |
| aortic aneurysm | Dangeous ballooning of the aorta (the main artery leaving the heart) which is caused by disease in the artery's wall. (09 Oct 1997) |
| aortic aneurysm, abdominal | An aneurysm in that part of the aorta continuing from the thoracic region and giving rise to the inferior phrenic, lumbar, median sacral, mesenteric, renal, and ovarian or testicular arteries. (12 Dec 1998) |
| aortic aneurysm, thoracic | An aneurysm in the proximal portion of the descending aorta proceeding from the arch of the aorta and giving rise to the bronchial, oesophageal, pericardiac, and mediastinal branches. (12 Dec 1998) |
| aortic arch | The curved portion between the ascending and descending parts of the aorta; it begins as a continuation of the ascending aorta posterior to the sternal angle, runs posteriorly and slightly to the left as it passes over the root of the left lung, and becomes the descending aorta as it reaches and begins to course along the vertebral column; it gives rise to the brachiocephalic trunk, the left common carotid and left subclavian arteries. Any member of the several pairs of arterial channels encircling the embryonic pharynx in the mesenchyme of the brachial arches; there are potentially six pairs, but in mammals the fifth pair is poorly developed or absent. The first and second pairs are functional only in very young embryos; the third pair is involved in the formation of the carotids; the fourth arch on the left is incorporated in the arch of the aorta; the sixth pair forms the proximal part of the pulmonary arteries. A series of arterial channels encircling the embryonic pharynx in the mesenchyme of the branchial arch's. There are potentially six pairs, but in mammals the fifth pair is poorly developed or absent. The first and second pairs are functional only in very young embryos; the third pair is involved in the formation of the carotids; the fourth arch on the left is incorporated in the arch of the aorta; the sixth pair forms the proximal part of the pulmonary arteries. Synonym: arcus aortae. (05 Mar 2000) |
| aortic arch syndrome | <syndrome> Aortic arch syndrome, also referred to by many as vertebral-basilar artery disease, carotid artery occlusive syndrome and subclavian steal syndrome is characterised by a constellation of signs and symptoms which occur secondary to abnormalities in the major arteries which extend off of the aortic arch. These abnormalities are structural and most often secondary to the effects of atherosclerosis, blood clots, trauma or a congenital abnormality. Symptoms of this condition include various neurologic symptoms, reduction in pulse and changes in blood pressure. (27 Sep 1997) |
| aortic arch syndromes | Any of a group of disorders leading to occlusion of the arteries arising from the aortic arch. Such occlusion may be caused by atherosclerosis, arterial embolism, syphilitic or tuberculous arteritis, etc. (12 Dec 1998) |
| aortic area | The region of the chest wall over the second right costal cartilage, where sounds produced at the aortic orifice are often best heard. (05 Mar 2000) |