| 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) |
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| 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) |
| spiral vein of modiolus | The vein running a spiral course in the modiolus of the cochlea; it is tributary to both the labyrinthine vein and the vein of the cochlear canaliculus. Synonym: vena spiralis modioli. (05 Mar 2000) |
| distal spiral septum | See: spiral septum. (05 Mar 2000) |
| internal spiral sulcus | A concavity in the floor of the cochlear duct formed by the overhanging labium vestibulare. Synonym: sulcus spiralis internus. (05 Mar 2000) |
| external spiral sulcus | A concavity in the outer wall of the cochlear duct between the prominentia spiralis and the spiral organ. Synonym: sulcus spiralis externus. (05 Mar 2000) |
| alar lamina of neural tube | The dorsal division of the lateral walls of the neural tube in the embryo; it gives rise to neurons relaying afferent impulses to higher centres; in the adult such neurons compose the sensory nuclei of the spinal cord and brainstem. Synonym: lamina alaris, alar plate of neural tube, dorsolateral plate of neural tube, lamina dorsalis, wing plate. (05 Mar 2000) |
| basal lamina | <cell biology> Extracellular matrix characteristically found under epithelial cells. There are two distinct layers: the basal lamina, immediately adjacent to the cells, is a product of the epithelial cells themselves and contains collagen type IV and the reticular lamina is produced by fibroblasts of the underlying connective tissue and contains fibrillar collagen. (15 Nov 1997) |
| basal lamina of choroid | The transparent, nearly structureless inner layer of the choroid in contact with the pigmented layer of the retina. Synonym: basal lamina of choroid, basal layer of choroid, Bruch's membrane, Henle's membrane, lamina vitrea, vitreous lamella, vitreous membrane. (05 Mar 2000) |