| SAX-PM | short-axis plane, papillary muscle |
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| SC | conditioned stimulus; sacrococcygeal; Sanitary Corps; scalenus [muscle]; scapula; Schwann cell; scia... |
| SM | Master of Science; sadomasochism; self-monitoring; silicon microphysiometer; simple mastectomy; skim... |
| SMA | sequential multiple analysis or analyzer; sequential multichannel autoanalyzer; simultaneous multich... |
| SMAF | smooth muscle activating factor; specific macrophage arming factor |
| smaller psoas muscle | <anatomy> An inconstant muscle, absent in about 40%; origin, bodies of twelfth thoracic and first lumbar vertebrae and disk between them; insertion, iliopubic eminence via iliopectineal arch (iliac fascia); action, assists in flexion of lumbar spine; nerve supply, lumbar plexus. Synonym: musculus psoas minor, smaller psoas muscle. (05 Mar 2000) |
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| smallest scalene muscle | <anatomy> An occasional independent muscular fasciculus between the scalenus anterior and medius, and having the same action and innervation. Synonym: musculus scalenus minimus, Albinus' muscle, Sibson's muscle, smallest scalene muscle. (05 Mar 2000) |
| smooth muscle | <anatomy, pathology, physiology> Muscle tissue in vertebrates made up from long tapering cells that may be anything from 20-500m long. Smooth muscle is generally involuntary and differs from striated muscle in the much higher actin/myosin ratio, the absence of conspicuous sarcomeres and the ability to contract to a much smaller fraction of its resting length. Smooth muscle cells are found particularly in blood vessel walls, surrounding the intestine (particularly the gizzard in birds) and in the uterus. The contractile system and its control resemble those of motile tissue cells (e.g. Fibroblasts, leucocytes) and antibodies against smooth muscle myosin will cross react with myosin from tissue cells, whereas antibodies against skeletal muscle myosin will not. See: dense bodies. (18 Nov 1997) |
| smooth muscle relaxant | An agent, such as an antispasmodic, bronchodilator, or vasodilator, that reduces the tension or tone of smooth (involuntary) muscle. (05 Mar 2000) |
| smooth muscle tissue | <anatomy, pathology, physiology> Muscle tissue in vertebrates made up from long tapering cells that may be anything from 20-500m long. Smooth muscle is generally involuntary and differs from striated muscle in the much higher actin/myosin ratio, the absence of conspicuous sarcomeres and the ability to contract to a much smaller fraction of its resting length. Smooth muscle cells are found particularly in blood vessel walls, surrounding the intestine (particularly the gizzard in birds) and in the uterus. The contractile system and its control resemble those of motile tissue cells (e.g. Fibroblasts, leucocytes) and antibodies against smooth muscle myosin will cross react with myosin from tissue cells, whereas antibodies against skeletal muscle myosin will not. See: dense bodies. (18 Nov 1997) |
| smooth muscle tumour | A tumour composed of smooth muscle tissue, as opposed to leiomyoma, a tumour derived from smooth muscle. (12 Dec 1998) |
| Soemmerring's muscle | A fasciculus occasionally passing from the thyrohyoid muscle to the isthmus of the thyroid gland. Synonym: musculus levator glandulae thyroideae, elevator muscle of thyroid gland, Soemmerring's muscle. (05 Mar 2000) |
| sphincter muscle | <anatomy> A ringlike band of muscle fibres that constricts a passage or closes a natural orifice, also called musculus sphincter. Origin: L., Gr. Sphinkter = that which binds tight (18 Nov 1997) |
| sphincter muscle of common bile duct | Smooth muscle sphincter of the common bile duct immediately proximal to the hepatopancreatic ampulla; it is this sphincter that controls the flow of bile in the duodenum. Synonym: musculus sphincter ductus choledochi, Boyden's sphincter, choledochal sphincter, sphincter muscle of common bile duct. (05 Mar 2000) |
| sphincter muscle of pancreatic duct | Smooth muscle sphincter of the main pancreatic duct immediately proximal to the hepatoduodenal, ampulla. Synonym: musculus sphincter ductus pancreatici, pancreatic sphincter, sphincter muscle of pancreatic duct. (05 Mar 2000) |
| sphincter muscle of pupil | A ring of smooth muscle fibres surrounding the pupillary border of the iris. Synonym: musculus sphincter pupillae, sphincter muscle of pupil. (05 Mar 2000) |
| sphincter muscle of pylorus | A thickening of the circular layer of the gastric musculature encircling the gastroduodenal junction. Synonym: musculus sphincter pylori, sphincter muscle of pylorus. (05 Mar 2000) |
| sphincter muscle of urethra | Origin, ramus of pubis; insertion, with fellow in median raphe behind and in front of urethra; action, constricts membranous urethra; nerve supply, pudendal. Synonym: musculus sphincter urethrae, external urethral sphincter, Guthrie's muscle, musculus compressor urethrae, musculus constrictor urethrae, musculus sphincter urethrae membranaceae, sphincter muscle of urethra, Wilson's muscle. (05 Mar 2000) |
| sphincter muscle of urinary bladder | The complete collar of smooth muscle cells of the neck of the urinary bladder which extend distally to surround the preprostatic sportion of the male urethra. There is not a comparable structure in the neck of the femoral bladder; the internal urethral sphincter may exist to prevent reflux of semen into bladder. Synonym: annulus urethralis, internal urethral sphincter, musculus sphincter vesicae, preprostate urethral sphincter, proximal urethral sphincter, sphincter muscle of urinary bladder. (05 Mar 2000) |
| spinalis capitis muscle | <anatomy> An inconstant extension of spinalis cervicis to the occipital bone, sometimes fusing with semispinalis capitis. Synonym: musculus spinalis capitis, biventer cervicis, spinal muscle of head. (05 Mar 2000) |