| 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) |
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| 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 ductus thoracici | See: thoracic duct. (05 Mar 2000) |
| arcus glossopalatinus | 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) |
| arcus iliopectineus | A thickened band of fused iliac and psoas fascia passing from the posterior aspect of the inguinal ligament anteriorly across the front of the femoral nerve to attach to the iliopectineal eminence of the hip bone posteriorly. The iliopectinal arch thus forms a septum which subdivides the space deep to the inguinal ligament into a lateral muscular lacunae and a medial vascular lacunae. When a psoas minor muscle is present, its tendon of insertion blends with the iliopectineal arch. Synonym: arcus iliopectineus, iliopectineal ligament, ligamentum iliopectineale. (05 Mar 2000) |
| arcus inguinalis | An alternate term for inguinal ligament. (05 Mar 2000) |
| arcus juvenilis | 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 lipoides | 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 lumbocostalis lateralis | <anatomy> One of Haller's arches; a thickening of the fascia of the quadratus lumborum muscle between the transverse process of the first lumbar vertebra and the twelfth rib on either side that gives attachment to a portion of the diaphragm. Synonym: ligamentum arcuatum laterale, arcus lumbocostalis lateralis, lateral lumbocostal arch. (05 Mar 2000) |
| arcus lumbocostalis medialis | <anatomy> One of Haller's arches; a tendinous thickening of the psoas fascia that extends from the body of the first lumbar vertebra to its transverse process on either side. A portion of the diaphragm arises from it. Synonym: ligamentum arcuatum mediale, arcus lumbocostalis medialis, medial lumbocostal arch. (05 Mar 2000) |
| arcus palatini | See: palatoglossal arch, palatopharyngeal arch. (05 Mar 2000) |
| arcus palatoglossus | 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) |