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Medical Dictionary


simulator (sim′u-la-ter, tor)
An apparatus designed to produce effects simulating those of specific environmental conditions; used in experimentation and training.

Simulium (si-mu′le-um)
A genus of biting gnats or midges, the black flies, humpbacked flies, or buffalo gnats in the dipteran family Simuliidae. The aquatic larvae require swift-flowing streams or highly oxygenated waters for their development, a critical epidemiologic factor in the role of these flies as disease vectors. In Central and South America, Mexico, and across central Africa, various species transmit Onchocerca volvulus, agent of human onchocerciasis. SYN: Eusimulium. [L. simulo, to simulate] S. damnosum species that is an important vector of onchocerciasis in central Africa. S. neavei species that is an important vector of onchocerciasis in eastern Africa where its larvae and pupae are attached to the shells of crabs of the genus Potamonantes. S. ochraceum species that is a vector of human onchocerciasis in Central America. S. rugglesi species that is a vector of Leucocytozoon simondi in Canada and the northern U.S.

simultagnosia (si-mul-tag-no′se-a)
SYN: simultanagnosia.

simultanagnosia (si-mul-tan-ag-no′se-a)
Inability to recognize multiple elements in a visual presentation, i.e., one object or some elements of a scene can be appreciated but not the display as a whole. SYN: simultagnosia. [simultaneous + agnosia]

Abbreviation for synchronized intermittent mandatory ventilation.

simvastatin (sim′va-sta-tin)
A potent HMG-CoA reductase (the rate-limiting enzyme for cholesterol biosynthesis) inhibitor. Used for the treatment of hyperlipidemia; similar to lovastatin.

sincalide (sin′ka-lid)
The C-terminal octapeptide of cholecystokinin; it causes smooth muscle contraction of the gallbladder and small intestine, relaxation of the choledoduodenal junction, and stimulates pancreatic and gastric secretions; also used as a diagnostic aid to retrieve bile for analysis.

sincipital (sin-sip′i-tal)
Relating to the sinciput.

sinciput, pl .sincipitasinciputs (sin′si-put, sin-sip′i-ta)
forehead. [L. half of the head]

Abbreviation for short interspersed elements, under element.

sinew (sin′oo)
SYN: tendon. [A.S. sinu]

Mark I., U.S. laryngologist, *1945. See Blom-S. valve.

singleton (sing′gel-tun)
1. A fetus that develops alone. 2. SYN: sport. [unknown]

singultation (sing′gul-ta′shun)
Hiccupping. See hiccup. [L. singulto, pp. -atus, to hiccup]

singultous (sing-gul′tus)
Relating to hiccups.

singultus (sing-gul′tus)
SYN: hiccup. [L.]

sinigrase, sinigrinase (sin′i-gras, -gri-nas)
SYN: thioglucosidase.

sinister (si-nis′ter) [TA]
Left. [L.]

sinistrad (sin′is-trad, si-nis′trad)
Toward the left side. [L. sinister, left, + ad, to]

sinistral (sin′is-tral, si-nis′tral)
1. Relating to the left side. SYN: sinistrous. 2. Denoting a left-handed person.

sinistrality (sin-is-tral′i-te)
The condition of being left-handed.

Left, toward the left. [L. sinister]

sinistrocardia (sin′is-tro-kar′de-a)
Displacement of the heart beyond the normal position on the left side. [sinistro- + G. kardia, heart]

sinistrocerebral (sin′is-tro-ser′e-bral)
Relating to the left cerebral hemisphere. [sinistro- + L. cerebrum, brain]

sinistrocular (sin-is-trok′u-lar)
Seldom-used term denoting one who prefers the left eye in monocular work, such as in the use of a microscope. Cf.:dominant eye. [sinistro- + L. oculus, eye]

sinistrogyration (sin′is-tro-ji-ra′shun)
SYN: sinistrotorsion. [sinistro- + L. gyratio, a turning around (gyration)]

sinistromanual (sin′is-tro-man′u-al)
SYN: left-handed. [sinistro- + L. manus, hand]

sinistropedal (sin-is-trop′e-dal)
Denoting one who uses the left leg by preference. SYN: left-footed. [sinistro- + L. pes (ped-), foot]

sinistrorotation (sin′is-tro-ro-ta′shun)
SYN: sinistrotorsion.

sinistrorse (sin′is-trors)
Turned or twisted to the left. [L. sinistrorsus, on the left side, fr. sinister, left, + verto, pp. versus, to turn]

sinistrotorsion (sin′is-tro-tor′shun)
A turning or twisting to the left. SYN: levocycleduction, levorotation (2) , levotorsion (1) , sinistrogyration, sinistrorotation. [sinistro- + L. torsio, a twisting (torsion)]

sinistrous (sin′is-trus, si-nis′trus)
SYN: sinistral (1) .

sinoatrial (si′no-a′tre-al)
SYN: sinuatrial.

sinography (si-nog′ra-fe)
Radiologic use of a contrast medium to opacify a sinus tract. [sinus + G. grapho, to write]

sinopulmonary (si′no-pul′mo-nar-e)
Relating to the paranasal sinuses and the pulmonary airway.

sinovaginal (si-no-vaj′i-nal)
Relating to that part of the vagina derived from the urogenital sinus.

sinter (sin′ter)
To heat a powdered substance without thoroughly melting it, causing it to fuse into a solid but porous mass. [Ger. dross, slag]

sinuatrial (S-A) (sin′u-a′tre-al, si′noo-)
Relating to the sinus venosus and the right atrium of the heart. SYN: sinoatrial.

sinus, pl .sinussinuses (si′nus, -ez)
1. [TA] A channel for the passage of blood or lymph, without the coats of an ordinary vessel; e.g., blood passages in the gravid uterus or those in the cerebral meninges. 2. [TA] A cavity or hollow space in bone or other tissue. 3. [TA] A dilation in a blood vessel. 4. A fistula or tract leading to a suppurating cavity. [L. s., cavity, channel, hollow] s. alae parvae SYN: sphenoparietal s.. anal sinuses [TA] 1. the grooves between the anal columns; SYN: Morgagni s. (1) . 2. pockets or crypts in the columnar zone of the anal canal between the anocutaneous line and the anorectal line; the sinuses give the mucosa a scalloped appearance. SYN: s. anales [TA] , anal crypts, Morgagni crypts, rectal sinuses. s. anales [TA] SYN: anal sinuses. anterior sinuses SYN: anterior ethmoidal cells, under cell. s. aortae [TA] SYN: aortic s.. aortic s. [TA] the space between the superior aspect of each cusp of the aortic valve and the dilated portion of the wall of the ascending aorta, immediately above each cusp. SYN: s. aortae [TA] , Petit s., Valsalva s.. Arlt s. an inconstant depression on the lower portion of the internal surface of the lacrimal sac. barber pilonidal s. pilonidal s. occurring in barbers, usually in the web between the fingers, due to the burying of exogenous hairs by the alternate loosening and tightening of tissues of the hand by the manipulation of scissors. basilar s. SYN: basilar venous plexus. Breschet s. SYN: sphenoparietal s.. s. caroticus [TA] SYN: carotid s.. carotid s. [TA] a slight dilation of the common carotid artery at its bifurcation into external and internal carotids; it contains baroreceptors that, when stimulated, cause slowing of the heart, vasodilation, and a fall in blood pressure and is innervated primarily by the glossopharyngeal nerve. SYN: s. caroticus [TA] , carotid bulb. s. cavernosus [TA] SYN: cavernous s.. cavernous s. [TA] a paired dural venous s. on either side of the sella turcica, the two being connected by anastomoses, the anterior intercavernosus s. (s. intercavernosus anterior [TA]) and posterior intercavernosus s. [TA] (s. intercavernosus posterior [TA]), in front of and behind the hypophysis, respectively, making thus the circular s.; the cavernous s. is unique among dural venous sinuses in being trabeculated; coursing within the s. are the internal carotid artery and the abducent nerve. SYN: s. cavernosus [TA] . cerebral sinuses SYN: dural venous sinuses. cervical s. in young mammalian embryos a depression in the nuchal region caudal to the hyoid arch, with the third and fourth branchial arches and ectodermal grooves in its floor; normally it is obliterated after the second month, but occasionally cervical fistulae persist as vestiges of it. SYN: precervical s.. circular s. 1. dural venous formation that surrounds the hypophysis, composed of right and left cavernous sinuses and the intercavernous sinuses; SYN: circulus venosus ridleyi, Ridley circle. 2. a venous s. at the periphery of the placenta; 3. SYN: scleral venous s.. s. circularis SYN: scleral venous s.. coccygeal s. a fistula opening in the region of the coccyx. SEE ALSO: pilonidal s.. s. coronarius [TA] SYN: coronary s.. coronary s. [TA] a short trunk receiving most of the cardiac veins, beginning at the junction of the great cardiac vein and the oblique vein of the left atrium, running in the posterior part of the coronary sulcus and emptying into the right atrium between the inferior vena cava and the atrioventricular orifice. SYN: s. coronarius [TA] . costomediastinal s. SYN: costomediastinal recess. cranial sinuses SYN: dural venous sinuses. dermal s. a s. lined with epidermis and skin appendages extending from the skin to some deeper-lying structure, most frequently the spinal cord. s. durae matris [TA] SYN: dural venous sinuses. dural venous sinuses [TA] endothelium-lined venous channels in the dura mater. SYN: s. durae matris [TA] , cerebral sinuses, cranial sinuses, sinuses of dura mater, venous sinuses. sinuses of dura mater SYN: dural venous sinuses. Englisch s. SYN: inferior petrosal s.. s. epididymidis [TA] SYN: s. of epididymis. s. of epididymis [TA] a narrow space between the body of the epididymis and the testis. SYN: s. epididymidis [TA] . ethmoidal sinuses SYN: ethmoid cells, under cell. s. ethmoidales SYN: ethmoid cells, under cell. s. ethmoidales anteriores SYN: anterior ethmoidal cells, under cell. s. ethmoidales mediae SYN: middle ethmoidal cells, under cell. s. ethmoidales posteriores SYN: posterior ethmoidal cells, under cell. frontal s. [TA] a hollow paranasal s. formed on either side in the lower part of the squama of the frontal bone; it communicates by the ethmoidal infundibulum with the middle meatus of the nasal cavity of the same side. SYN: s. frontalis [TA] . s. frontalis [TA] SYN: frontal s.. Guérin s. a cul-de-sac or diverticulum behind the valve of the navicular fossa. Huguier s. SYN: fossa of oval window. inferior longitudinal s. SYN: inferior sagittal s.. inferior petrosal s. [TA] a paired dural venous s. running in the groove on the petrooccipital fissure connecting the cavernous s. with the superior bulb of the internal jugular vein. SYN: s. petrosus inferior [TA] , Englisch s.. inferior sagittal s. [TA] an unpaired dural venous s. in the lower margin of the falx cerebri, running parallel to the superior sagittal s. and merging with the great cerebral vein to form the straight s.. SYN: s. sagittalis inferior [TA] , inferior longitudinal s.. s. intercavernosi anterior et posterior [TA] SYN: intercavernous sinuses. intercavernous sinuses the anterior and posterior anastomoses between the cavernous sinuses, passing anterior and posterior to the hypophysis and forming, with the cavernous sinuses, the circular s.. SEE ALSO: cavernous s.. SYN: s. intercavernosi anterior et posterior [TA] , Ridley s.. jugular s., s. jugularis one of three enlargements of the jugular veins; the external jugular s. is between the two sets of valves; the internal jugular sinuses are at the origin (superior bulb) and near the termination (inferior bulb). s. lactiferi [TA] SYN: lactiferous s.. lactiferous s. [TA] a circumscribed spindle-shaped dilation of the lactiferous duct just before it enters the nipple. In nursing mothers, this dilation stores a droplet of milk that is expressed by compression as the infant begins to suckle; this is thought to encourage continual suckling while the let-down reflex ensues. SYN: s. lactiferi [TA] , ampulla lactifera, ampulla of lactiferous duct, ampulla of milk duct, lactiferous ampulla. laryngeal s. SYN: laryngeal ventricle. s. laryngeus SYN: laryngeal ventricle. lateral s. SYN: transverse s.. s. lienis SYN: splenic s.. longitudinal s. inferior sagittal s., superior sagittal s.. longitudinal vertebral venous s. large, plexiform veins forming portions of the anterior internal vertebral venous plexus lying on the posterior surfaces of the vertebral bodies on either side of the posterior longitudinal ligament. SYN: s. vertebrales longitudinales. Luschka s. venous s. in the petrosquamous suture. lymph s. SYN: lymphatic s.. lymphatic s. the channels in a lymph node crossed by a reticulum of cells and fibers and bounded by littoral cells; there are subcapsular, trabecular, and medullary sinuses. SYN: lymph s.. Maier s. an infundibuliform depression on the internal surface of the lacrimal sac which receives the lacrimal canaliculi. marginal sinuses of placenta discontinuous venous lakes at the margin of the placenta. mastoid sinuses SYN: mastoid cells, under cell. s. maxillaris [TA] SYN: maxillary s.. maxillary s. [TA] the largest of the paranasal sinuses occupying the body of the maxilla, communicating with the middle meatus of the nose. SYN: s. maxillaris [TA] , antrum of Highmore, genyantrum, maxillary antrum. Meyer s. a small concavity in the floor of the external auditory canal near the membrana tympani. middle ethmoidal sinuses SYN: middle ethmoidal cells, under cell. Morgagni s. 1. SYN: anal sinuses (1) . 2. SYN: prostatic utricle. 3. SYN: laryngeal ventricle. s. of nail SYN: s. unguis. oblique pericardial s. [TA] the recess in the pericardial cavity posterior to the base of the heart bounded laterally by the pericardial reflections on the pulmonary veins and inferior vena cava, and posteriorly by the pericardium overlying the anterior aspect of the esophagus. SYN: s. obliquus pericardii [TA] , oblique s. of pericardium. oblique s. of pericardium SYN: oblique pericardial s.. s. obliquus pericardii [TA] SYN: oblique pericardial s.. occipital s. [TA] an unpaired dural venous s. commencing at the confluence of the sinuses and passing downward in the base of the falx cerebelli to the foramen magnum. SYN: s. occipitalis [TA] . s. occipitalis [TA] SYN: occipital s.. Palfyn s. a space within the crista galli of the ethmoid described as communicating with the ethmoidal and frontal sinuses. paranasal sinuses [TA] the paired air-filled cavities in the bones of the face lined by mucous membrane continuous with that of the nasal cavity; these sinuses are the frontal, sphenoidal, maxillary, and ethmoidal. SYN: s. paranasales [TA] . s. paranasales [TA] SYN: paranasal sinuses. parasinoidal sinuses SYN: lateral lacunae of superior sagittal s., under lacuna. Petit s. SYN: aortic s.. petrosal s. inferior petrosal s., superior petrosal s.. s. petrosus inferior [TA] SYN: inferior petrosal s.. s. petrosus superior [TA] SYN: superior petrosal s.. phrenicocostal s. SYN: costodiaphragmatic recess. pilonidal s. a fistula or pit in the sacral region, communicating with the exterior, containing hair which may act as a foreign body producing chronic inflammation. SYN: pilonidal fistula. piriform s. SYN: piriform fossa. pleural sinuses SYN: pleural recesses, under recess. s. pocularis SYN: prostatic utricle. s. posterior cavi tympani [TA] SYN: posterior s. of tympanic cavity. posterior s. of tympanic cavity [TA] a deep groove above the pyramidal eminence extending to the incudal fossa in the posterior wall of the tympanic cavity. SYN: s. posterior cavi tympani [TA] . preauricular s. s. tract or pit in preauricular skin, resulting from developmental defect of the first and second branchial arches. SYN: preauricular pit. precervical s. SYN: cervical s.. prostatic s. [TA] the groove on either side of the urethral crest in the prostatic part of the urethra into which the prostatic ducts open. SYN: s. prostaticus [TA] . s. prostaticus [TA] SYN: prostatic s.. pulmonary sinuses SYN: s. of pulmonary trunk. s. of pulmonary trunk [TA] the space at the origin of the pulmonary trunk between the dilated wall of the vessel and each cusp of the pulmonic valve. SYN: s. trunci pulmonalis [TA] , pulmonary sinuses. rectal sinuses SYN: anal sinuses. s. rectus [TA] SYN: straight s.. renal s. [TA] the cavity of the kidney, containing the calices and pelvis of the ureter and the segmental vesels embedded within a fatty matrix. The renal sinuses cause the kidneys to appear hollow or C-shaped on cross section or medical imaging. SYN: s. renalis [TA] . s. renalis [TA] SYN: renal s.. s. reuniens obsolete term for s. venosus. rhomboidal s., s. rhomboidalis a dilation of the central canal of the spinal cord in the lumbar region. SYN: rhombocele. Ridley s. SYN: intercavernous sinuses. Rokitansky-Aschoff sinuses small outpocketings of the mucosa of the gallbladder which extend through the muscular layer; they may be congenital. s. sagittalis inferior [TA] SYN: inferior sagittal s.. s. sagittalis superior [TA] SYN: superior sagittal s.. scleral venous s. [TA] the vascular structure encircling the anterior chamber of the eye and through which the aqueous is returned to the blood circulation. SYN: s. venosus sclerae [TA] , circular s. (3) , Fontana canal, Lauth canal, Schlemm canal, s. circularis, venous s. of sclera. sigmoid s. [TA] the S-shaped dural venous s. lying deep to the mastoid process of the temporal bone and immediately posterior to the petrous temporal bone; it is continuous with the transverse s. and empties into the internal jugular vein as it passes through the jugular foramen. SYN: s. sigmoideus [TA] . s. sigmoideus [TA] SYN: sigmoid s.. sphenoidal s. [TA] one of a pair of paranasal sinuses in the body of the sphenoid bone communicating with the upper posterior nasal cavity or sphenoethmoidal recess. SYN: s. sphenoidalis [TA] . s. sphenoidalis [TA] SYN: sphenoidal s.. sphenoparietal s. [TA] a paired dural venous s. beginning on the parietal bone, running along the sphenoidal ridges and emptying into the cavernous s.. SYN: s. sphenoparietalis [TA] , Breschet s., s. alae parvae. s. sphenoparietalis [TA] SYN: sphenoparietal s.. splenic s. an elongated venous channel, 12–40 μm wide, lined by rod-shaped cells. SYN: s. lienis. straight s. [TA] an unpaired dural venous s. in the posterior part of the falx cerebri where it is attached to the tentorium cerebelli; it is formed anteriorly by the merging of the great cerebral vein with the inferior sagittal s., and passes horizontally and posteriorly to the confluence of sinuses. SYN: s. rectus [TA] , tentorial s.. superior longitudinal s. SYN: superior sagittal s.. superior petrosal s. [TA] a paired dural venous s. in the groove along the crest of the petrous temporal bone, connecting the cavernous s. with the termination of the transverse s. or beginning of the sigmoid s.. SYN: s. petrosus superior [TA] . superior sagittal s. [TA] an unpaired dural venous s. in the sagittal groove, beginning at the foramen caecum and terminating at the confluence of sinuses where it merges with the straight s.; receives the superior cerebral veins and has lateral extensions, the lateral venous lacunae. SYN: s. sagittalis superior [TA] , superior longitudinal s.. tarsal s. [TA] a hollow or canal formed by the groove of the talus and the interosseous groove of the calcaneus that is occupied by the interosseous talocalcaneal ligament. SYN: s. tarsi [TA] , tarsal canal. s. tarsi [TA] SYN: tarsal s.. tentorial s. SYN: straight s.. terminal s., s. terminalis the vein bounding the area vasculosa in the blastoderm. s. tonsillaris SYN: tonsillar fossa. Tourtual s. SYN: supratonsillar fossa. transverse s. [TA] a paired dural venous s. that drains the confluence of sinuses, running along the occipital attachment of the tentorium cerebelli and terminating in the sigmoid s.. SYN: s. transversus [TA] , lateral s.. transverse pericardial s. [TA] a passage in the pericardial sac between the origins of the great vessels, i.e., posterior to the intrapericardial portions of the pulmonary trunk and ascending aorta and anterior to the superior vena cava and superior to the atria; it is formed as a result of the flexure of the heart tube, partially approximating the great venous and arterial vessels. SYN: s. transversus pericardii [TA] , Theile canal, transverse s. of pericardium. transverse s. of pericardium SYN: transverse pericardial s.. s. transversus [TA] SYN: transverse s.. s. transversus pericardii [TA] SYN: transverse pericardial s.. s. trunci pulmonalis [TA] SYN: s. of pulmonary trunk. s. tympani [TA] SYN: tympanic s.. tympanic s. [TA] a depression in the tympanic cavity posterior to the tympanic promontory. SYN: s. tympani [TA] . s. unguis the deep cleft housing the root of the nail. SYN: s. of nail. urogenital s. 1. the ventral part of the cloaca after its separation from the rectum by the growth of the urorectal septum; from it develops the lower part of the bladder in both sexes, the prostatic portion of the male urethra, and the urethra and vestibule in the female; 2. SYN: persistent cloaca. s. urogenitalis SYN: persistent cloaca. uterine s. a small irregular vascular channel in the endometrium, of a type that forms during pregnancy. SYN: uterine sinusoid. uteroplacental sinuses irregular vascular spaces in the zone of the chorionic attachment to the decidua basalis. Valsalva s. SYN: aortic s.. s. of the vena cava [TA] the portion of the cavity of the right atrium of the heart that receives the blood from the venae cavae; it is separated from the rest of the atrium by the crista terminalis. SYN: s. venarum cavarum [TA] . s. venarum cavarum [TA] SYN: s. of the vena cava. s. venosus [TA] a cavity at the caudal end of the embryonic cardiac tube in which the veins from the intra- and extraembryonic circulatory arcs unite; in the course of development it forms the portion of the right atrium known in adult anatomy as the s. of the vena cava. SYN: saccus reuniens. s. venosus sclerae [TA] SYN: scleral venous s.. venous sinuses SYN: dural venous sinuses. venous s. of sclera SYN: scleral venous s.. s. vertebrales longitudinales SYN: longitudinal vertebral venous s..

sinusitis (si-nu-si′tis)
Inflammation of the mucous membrane of any sinus, especially of one of the paranasal sinuses. [sinus + G. -itis, inflammation]

sinusoid (si′nu-soyd)
1. Resembling a sinus. 2. Sinusoidal capillary; a thin-walled terminal blood vessel having an irregular and larger caliber than an ordinary capillary; its endothelial cells have large gaps and the basal lamina is either discontinuous or absent. SYN: sinusoidal capillary. [sinus + G. eidos, resemblance] uterine s. SYN: uterine sinus.

sinusoidal (si-nu-soy′dal)
Relating to a sinusoid.

sinusotomy (sin-u-sot′o-me)
Incision into a sinus. [sinus + G. tome, incision]

si op. sit
Abbreviation for L. si opus sit, if needed.

siphon (si′fon)
A tube bent into two unequal lengths, used to remove fluid from a cavity or vessel by atmospheric pressure. [G. s., tube]

siphonage (si′fon-ij)
Emptying of the stomach or other cavity by means of a siphon.

Siphona irritans (si-fo′na ir′i-tanz)
The horn fly, a bloodsucking muscoid fly that causes great irritation and annoyance to cattle, and transmits Stephanofilaria stilesi. [G. siphon, tube]

Siphonaptera (si-fo-nap′te-ra)
The fleas, an order of wingless insect ectoparasites highly adapted for survival in mammalian fur; they are flattened laterally, spined, and equipped with well-developed metathoracic legs for jumping. [G. siphon, tube, + G. a- priv. + pteron, wing]

Siphoviridae (sif′o-vi′ra-da)
A family of bacterial viruses with long, noncontractile tails and isometric or elongated heads, containing double-stranded DNA (MW 25–79 × 106); includes the λ temperate phage group and probably other genera. [L. sipho, little tube, pipe, fr. G. siphon, + virus]

John H., U.S. physician, *1930. See S. syndrome.

Bertram W., U.S. physician, 1866–1924. See S. diet.

sireniform (si-ren′i-form)
Denoting a malformation with the appearance of sirenomelia.


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