| SNR | selective nerve root [block]; signal-to-noise ratio; substantia nigra zona reticulata; supernumerary... |
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| substantia fundamentalis | The amorphous material in which structural elements occur; in connective tissue, it is composed of proteoglycans, plasma constituents, metabolites, water, and ions present between cells and fibres. Synonym: substantia fundamentalis. (05 Mar 2000) |
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| substantia gelatinosa | The apical part of the posterior horn (dorsal horn; posterior gray column) of the spinal cord's gray matter, composed largely of very small nerve cells; its gelatinous appearance is due to its very low content of myelinated nerve fibres. Synonym: substantia gelatinosa, Rolando's gelatinous substance, Rolando's substance. (05 Mar 2000) |
| substantia gelatinosa centralis | The central gray matter of the spinal cord surrounding the central canal. Synonym: substantia intermedia centralis et lateralis, anterior gray column, Stilling's gelatinous substance, substantia gelatinosa centralis. (05 Mar 2000) |
| substantia glandularis prostatae | The glandular tissue of the prostate as distinct from the stroma and capsule. Synonym: substantia glandularis prostatae. (05 Mar 2000) |
| substantia grisea | The cortex of the brain which contains nerve cell bodies. The gray matter is in contrast to the white matter, the part of the brain that contains myelinated nerve fibres. The gray matter is so named because it in fact appears gray. The white matter is white because that is the colour of myelin, the insulation covering the nerve fibres. In the mysterious affair at styles (1920), agatha christie first quoted the fictional belgian detective hercule poirot in regard to his gray matter: 'this affair must be unravelled from within.' he tapped his forehead. 'these little grey cells. It is up to them as you say over here.' (12 Dec 1998) |
| substantia grisea centralis | In general: the predominantly small-celled gray matter adjoining or surrounding the central canal of the spinal cord and the third and fourth ventricles of the brainstem, in particular: the thick sleeve of gray matter surrounding the cerebral sylvian aqueduct in the midbrain, rostrally continuous with the posterior nucleus of the hypothalamus; in sections stained for myelin it stands out from the adjoining tectum and tegmentum by the poverty of its myelinated fibres. Synonym: substantia grisea centralis. (05 Mar 2000) |
| substantia innominata | Tissue in the base of the forebrain inferior to the anterior perforated substance, and anterior to the globus pallidus and ansa lenticularis. It contains the nucleus basalis of meynert and may be implicated in alzheimer's disease. (12 Dec 1998) |
| substantia intermedia centralis et lateralis | The central gray matter of the spinal cord surrounding the central canal. Synonym: substantia intermedia centralis et lateralis, anterior gray column, Stilling's gelatinous substance, substantia gelatinosa centralis. (05 Mar 2000) |
| substantia lentis | That which constitutes the lens of the eye, composed of a nucleus and a cortex and covered by an epithelium. Synonym: substantia lentis. (05 Mar 2000) |
| substantia medullaris | The inner portion of an organ. (09 Oct 1997) |
| substantia muscularis prostatae | The smooth muscle in the stroma of the prostate. Synonym: substantia muscularis prostatae, musculus prostaticus. (05 Mar 2000) |
| substantia nigra | A large cell mass, crescentic on transverse section, extending forward over the dorsal surface of the crus cerebri from the rostral border of the pons into the subthalamic region; it is composed of a dorsal stratum of closely spaced pigmented (i.e., melanin-containing) cells, the pars compacta, and a larger ventral region of widely scattered cells, the pars reticulata; the pars compacta in particular includes numerous cells that project forward to the striatum (caudate nucleus and putamen) and contain dopamine, which acts as the transmitter substance at their synaptic endings; other, apparently non-dopaminergic cells of the substantia nigra project to a rostral part of the ventral nucleus of thalmus, the middle layers of the superior colliculus and to restricted parts of the reticular formation of the midbrain; the nigrostriatal projection is reciprocated by a massive striatonigral fibre system with multiple neurotransmitters, chief among which is gamma-aminobutyric acid (GABA); substantia n. Receives smaller afferent projections from the subthalamic nucleus, the lateral segment of the globus pallidus, the dorsal nucleus of the raphe and the pedunculopontine nucleus of the midbrain. The pars reticulata forms part of the output system for the striate body. The substantia n. Is involved in the metabolic disturbances associated with Parkinson's disease and Huntington's disease. Synonym: locus niger, nucleus niger, Soemmerring's ganglion. (05 Mar 2000) |
| substantia ossea dentis | <dentistry> A bony substance covering the root of a tooth. (08 Jan 1998) |
| substantia perforata anterior | A region at the base of the brain through which numerous small branches of the anterior and middle cerebral arteries (lenticulostriate arteries) enter the depth of the cerebral hemisphere; it is bordered medially by the optic chasm and anterior half of the optic tract, rostrally and laterally by the lateral olfactory stria; its anteromedial part corresponds to the olfactory tubercle. Synonym: substantia perforata anterior, locus perforatus anticus, olfactory area. (05 Mar 2000) |
| substantia perforata posterior | The bottom of the interpeduncular fossa at the base of the midbrain, extending from the anterior border of the pons forward to the mamillary bodies, and containing numerous openings for the passage of perforating branches of the posterior cerebral arteries. Synonym: substantia perforata posterior, locus perforatus posticus, Malacarne's space. (05 Mar 2000) |