| nodus suprapyloricus | A lymph node located above the pylorus. Synonym: nodus suprapyloricus, suprapyloric node. (05 Mar 2000) |
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| nodus tibialis anterior | A small inconstant lymph node in front of the interosseous membrane along the upper part of the anterior tibial vessels. Synonym: nodus tibialis anterior, anterior tibial node. (05 Mar 2000) |
| nodus tibialis posterior | A small inconstant lymph node located along the course of the posterior tibial artery. Synonym: nodus tibialis posterior, posterior tibial node. (05 Mar 2000) |
| nonreset nodus sinuatrialis | Nonreset of the sinoatrial node produced by a premature atrial depolarisaton when the sum of the duration of the premature cycle and the return cycle is fully compensatory, i.e., twice the duration of the spontaneous cycle length. Compare: reset nodus sinuatrialis. (05 Mar 2000) |
| arcus | Synonym: arch. Origin: L. A bow (05 Mar 2000) |
| arcus adiposus | 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) |
| arcus alveolaris mandibulae | The free margin of the alveolar process of the mandible. Synonym: arcus alveolaris mandibulae, limbus alveolaris. (05 Mar 2000) |
| arcus alveolaris maxillae | The free border of the alveolar process of the maxilla. Synonym: arcus alveolaris maxillae, limbus alveolaris. (05 Mar 2000) |
| arcus anterior atlantis | 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) |
| arcus aortae | 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) |
| arcus cartilaginis cricoideae | The narrow part of the cartilage that encircles the air passage anterior to the lamina. Synonym: arcus cartilaginis cricoideae. (05 Mar 2000) |
| arcus cornealis | 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) |
| arcus costalis | That portion of the inferior aperture of the thorax formed by the articulated cartilages of the seventh to tenth (false) ribs. Synonym: arcus costalis, arcus costarum. (05 Mar 2000) |
| arcus costarum | That portion of the inferior aperture of the thorax formed by the articulated cartilages of the seventh to tenth (false) ribs. Synonym: arcus costalis, arcus costarum. (05 Mar 2000) |
| arcus dentalis inferior | The teeth supported by the alveolar part of the mandible, whether the 10 deciduous teeth or the 16 permanent teeth. Synonym: arcus dentalis inferior, mandibular dentition. (05 Mar 2000) |