| Corti's 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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| critical organ | The organ or physiologic system that for a given source of radiation would first reach its legally defined maximum permissible radiation exposure as the dose of radiopharmaceutical is increased; e.g., the kidney is the critical organ when 197Hg-chlormerodrin is given. (05 Mar 2000) |
| ptotic organ | An organ with loose attachments, permitting its displacement. Synonym: floating organ, ptotic organ. (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) |
| neuromast organ | A structure in fish consisting of a long groove or canal extending along each side of the trunk and tail and branching in the head region; the groove or tube is lined with neuroepithelial cells, some of which are in groups known as neuromasts; its function appears to be the detection of vibrations of low frequency. Synonym: neuromast organ. (05 Mar 2000) |
| neurotendinous organ | <cell biology, physiology> A proprioceptive sensory nerve ending embedded among the fibres of a tendon, often near the musculotendinous junction; it is compressed and activated by any increase of the tendon's tension, caused either by active contraction or passive stretch of the corresponding muscle. Synonym: neurotendinous organ, neurotendinous spindle. (05 Mar 2000) |
| subcommissural organ | An ependymal derivative located at the junction of the third ventricle and the cerebral aqueduct, secreting somatostatin. (12 Dec 1998) |
| subfornical organ | A structure, situated close to the intraventricular foramen, which induces drinking behaviour after stimulation with angiotensin II. (12 Dec 1998) |
| intromittent organ | <anatomy> The male organ of copulation and of urinary excretion, comprising a root, body and extremity or glans penis. The root is attached to the descending portions of the pubic bone by the crura, the latter being the extremities of the corpora cavernosa and beneath them the corpus spongiosum, through which the urethra passes. The glans is covered with mucous membrane and ensheathed by the prepuce or foreskin. The penis is homologous with the clitoris in the female. (18 Nov 1997) |
| olfactory organ | The olfactory region in the superior portion of the nasal cavity. Synonym: organum olfactus, organ of smell. (05 Mar 2000) |
| organ | 1. An instrument or medium by which some important action is performed, or an important end accomplished; as, legislatures, courts, armies, taxgatherers, etc, are organs of government. 2. <biology> A natural part or structure in an animal or a plant, capable of performing some special action (termed its function), which is essential to the life or well-being of the whole; as, the heart, lungs, etc, are organs of animals; the root, stem, foliage, etc, are organs of plants. In animals the organs are generally made up of several tissues, one of which usually predominates, and determines the principal function of the organ. Groups of organs constitute a system. See System. 3. A component part performing an essential office in the working of any complex machine; as, the cylinder, valves, crank, etc, are organs of the steam engine. 4. A medium of communication between one person or body and another; as, the secretary of state is the organ of communication between the government and a foreign power; a newspaper is the organ of its editor, or of a party, sect, etc. 5. [Cf. AS. Organ, fr. L. Organum. A wind instrument containing numerous pipes of various dimensions and kinds, which are filled with wind from a bellows, and played upon by means of keys similar to those of a piano, and sometimes by foot keys or pedals; formerly used in the plural, each pipe being considired an organ. "The deep, majestic, solemn organs blow." (Pope) Chaucer used the form orgon as a plural. "The merry orgon . . . That in the church goon [go]" Barrel organ, Choir organ, Great organ, etc. See Barrel, Choir, etc. <anatomy> Cabinet organ, a passage in which the tonic or dominant is sustained continuously by one part, while the other parts move. Origin: L. Organum, Gr.; akin to work, and E. Work: cf. F. Organe. See Work, and cf. Orgue, Orgy. Source: Websters Dictionary (01 Mar 1998) |
| organ culture | <cell biology> Culture in vitro of pieces of tissue (as opposed to single cells) in such a way as to maintain some normal spatial relationships between cells and some normal function. Contrast with tissue culture. (18 Nov 1997) |
| organ of corti | The organ that contains the special sensory receptors for hearing. It is composed of a series of epithelial structures placed upon the inner part of the basilar membrane. (12 Dec 1998) |
| organ of hearing | The content of the cochlea including the portion of the membranous labyrinth containing the spiral organ (cochlear duct) and the perilymphatic channels (scalae) which lie on either side. Synonym: labyrinthus cochlearis, organ of hearing. (05 Mar 2000) |
| organ of Rosenmuller | <anatomy> See Parovarium. Origin: NL, from Gr. Upon + egg + to bear. Source: Websters Dictionary (01 Mar 1998) |