| RAI | radioactive iodine; radioactive isotope; resident assessment instrument; resting ankle index; right ... |
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| RAR | rapidly adapting receptor; rat insulin receptor; retinoic acid receptor; right arm reclining; right ... |
| RB | radiation burn; rating board; rebreathing; reticulate body; retinoblastoma; right bronchus; right bu... |
| RBA | relative binding affinity; rescue breathing apparatus; right basilar artery; right brachial artery; ... |
| RCA | red cell agglutination; relative chemotactic activity; renal cell carcinoma; right carotid artery; r... |
| spiral groove | <anatomy, nerve> The shallow groove that passes around the shaft of the humerus; it lodges the radial nerve and deep brachial artery. Synonym: sulcus nervi radialis, musculospiral groove, spiral groove. (05 Mar 2000) |
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| spiral hyphae | Hyphae that end in a flat or helical coil, as in laboratory colonies of Trichophyton mentagrophytes. (05 Mar 2000) |
| spiral joint | A variety of hinge joint in which the elevation and depression, respectively, on the opposing articular surfaces form part of a spiral, flexion being then accompanied by a certain amount of lateral deviation. Synonym: screw joint, spiral joint. (05 Mar 2000) |
| spiral lamina | The bony plate which extends outwards from the modiolus. It is part of the structure which divides trhe cochlea into sections. (12 Dec 1998) |
| spiral ligament of cochlea | The thickened periosteal lining of the bony cochlea forming the outer wall of the cochlear duct to which the basal lamina attaches. Synonym: crista spiralis, ligamentum spirale cochleae, spiral crest. (05 Mar 2000) |
| spiral line | A rough line that separates the neck and shaft of the femur anteriorly; it passes downward and medially from the greater trochanter to the lesser trochanter and continues into the medial lip of the linea aspera. Synonym: linea intertrochanterica, linea spiralis, spiral line. (05 Mar 2000) |
| spiral membrane | The wall that separates the cochlear duct from the scala tympani; it consists of the osseous spiral lamina and the basilar membrane. Synonym: paries tympanicus ductus cochlearis, membrana spiralis, spiral membrane. (05 Mar 2000) |
| spiral organ | A prominent ridge of highly specialised epithelium in the floor of the cochlear duct overlying the basilar membrane of cochlea, containing one inner row and three outer rows of hair cells, or cells of Corti (the auditory receptor cells innervated by the cochlear nerve) supported by various columnar cells: the pillars of Corti, cells of Hensen, and cells of Claudius; the spiral organ is partly overhung by an awning-like shelf, the tectorial membrane, the free marginal zone of which is covered by a gelatinous substance in which the stereocilia of the outer hair cells are embedded. Synonym: organum spirale, acoustic papilla, Corti's organ. (05 Mar 2000) |
| spiral plate | A double plate of bone winding spirally around the modiolus dividing the spiral canal of the cochlea incompletely into two, scala tympani and scala vestibuli; between the two plates of this lamina the fibres of the cochlear nerve reach the spiral organ (of Corti). Synonym: lamina spiralis ossea, spiral plate. (05 Mar 2000) |
| spiral prominence | A projecting portion of the spiral ligament of the cochlea, bounding the lower edge of the stria vascularis and containing within it a blood vessel, the vas prominens. Synonym: prominentia spiralis. (05 Mar 2000) |
| spiral septum | A septum dividing the embryonic bulbus cordis into pulmonary and aortic outflow tracts from the developing heart; the distal spiral septum is derived from the right and left endocardial cushions and so separates the pulmonary and aortic orifices; the proximal spiral septum is the portion of the septum that is incorporated into the membranous part of the interventricular septum. (05 Mar 2000) |
| spiral suture | An uninterrupted series of stitches using one suture; the stitching is fastened at each end by a knot. Synonym: spiral suture, uninterrupted suture. (05 Mar 2000) |
| spiral tip catheter | A catheter with a helical filiform tip. (05 Mar 2000) |
| spiral tubule | The segment of urinary tubule coming next after the proximal convoluted tubule. (05 Mar 2000) |
| spiral valve of cystic duct | A series of crescentic folds of mucous membrane in the upper part of the cystic duct, arranged in a somewhat spiral manner. Synonym: plica spiralis ductus cystici, Amussat's valve, Heister's valve, spiral valve of cystic duct, valvula spiralis. (05 Mar 2000) |