| lesser palatine nerves | Usually two, these nerves emerge through the lesser palatine foramina and supply the mucosa and glands of the soft palate and uvula; they are branches of the pterygopalatine ganglion and contain postsynaptic parasympathetic and sensory fibres of the maxillary nerve. Synonym: nervi palatini minores. (05 Mar 2000) |
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| abdominothoracic arch | A bell-shaped line defined by the lower end of the sternum and the costal arches on each side, constituting a boundary line between the anterolateral portions of the thoracic and abdominal walls. (05 Mar 2000) |
| alveolar arch of mandible | The free margin of the alveolar process of the mandible. Synonym: arcus alveolaris mandibulae, limbus alveolaris. (05 Mar 2000) |
| alveolar arch of maxilla | The free border of the alveolar process of the maxilla. Synonym: arcus alveolaris maxillae, limbus alveolaris. (05 Mar 2000) |
| anterior arch of atlas | An arch that connects the lateral masses of the atlas anteriorly and articulates with the anterior articular facet of the dens of the axis. Synonym: arcus anterior atlantis. (05 Mar 2000) |
| 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) |
| arch | <dentistry> Collectively, either the teeth or the basal bone of either jaw. (08 Jan 1998) |
| arch bar | Any one of several types of wires, bar's, or splints conforming to the arch of the teeth, extending from one side of the arch to the other and located labially, or lingually; used for the treatment of jaw fractures and/or stabilization of injured teeth. (05 Mar 2000) |
| arch length | The amount of space required for the permanent teeth as measured from the mesial aspect of the first molar on one side to the mesial aspect of the first molar on the opposite side, as measured through the contact points along an imaginary line of the dental arch. (05 Mar 2000) |
| arch length deficiency | The difference between the available circumference of the dental arch and that required to accommodate the succedaneous teeth in proper alignment. (05 Mar 2000) |
| arch-loop-whorl system | See: Galton's system of classification of fingerprints. (05 Mar 2000) |
| arch of cricoid cartilage | The narrow part of the cartilage that encircles the air passage anterior to the lamina. Synonym: arcus cartilaginis cricoideae. (05 Mar 2000) |
| arch of the aorta | 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) |