| sinus tubercle | A median protuberance projecting into the embryonic urogenital sinus from its dorsal wall; it is formed from the fused caudal ends of the paramesonephric ducts and is the first evidence of the embryonic uterus and vagina. Synonym: sinus tubercle. (05 Mar 2000) |
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| sinus tympani | A depression in the tympanic cavity posterior to the tympanic promontory. Synonym: sinus tympani. Sinus unguis, the deep cleft housing the root of the nail. Synonym: sinus of nail. (05 Mar 2000) |
| sinus urogenitalis | A condition in which the urorectal fold has failed to divide the cloaca of the embryo into rectal and urogenital portions. Synonym: sinus urogenitalis, urogenital sinus. (05 Mar 2000) |
| sinus venarum cavarum | 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. Synonym: sinus venarum cavarum. (05 Mar 2000) |
| sinus venosus | 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 sinus of the vena cava. Synonym: saccus reuniens. Sinus venosus sclerae, the vascular structure encircling the anterior chamber of the eye and through which the aqueous is returned to the blood circulation. Synonym: circular sinus, Fontana's canal, Lauth's canal, Schlemm's canal, sinus circularis, venous sinus of sclera. (05 Mar 2000) |
| sinus venosus syndrome | <syndrome> The association of partial anomalous, pulmonary-venous connection, and a small venosus ASD. (05 Mar 2000) |
| sinus vertebrales longitudinales | longitudinal vertebral venous sinus |
| sphenoidal sinus | One of a pair of paranasal sinuses in the body of the sphenoid bone communicating with the upper posterior nasal cavity or spenoethmoidal recess. Synonym: sinus sphenoidalis. (05 Mar 2000) |
| sphenoidal sinus aperture | One of the pair of openings in the body of the sphenoid bone through which the sphenoid sinuses communicate with the sphenoethmoidal recess of the nasal cavity. Synonym: apertura sinus sphenoidalis, sphenoidal sinus aperture. (05 Mar 2000) |
| sphenoid sinus | One of the paired paranasal sinuses, located in the body of the sphenoid bone and communicating with the highest meatus of the nasal cavity on the same side. (12 Dec 1998) |
| sphenoparietal sinus | A paired dural venous sinus beginning on the parietal bone, running along the sphenoidal ridges and emptying into the cavernous sinus. Synonym: sinus sphenoparietalis, Breschet's sinus, sinus alae parvae. (05 Mar 2000) |
| splenic sinus | An elongated venous channel, 12 to 40 um wide, lined by rod-shaped cells. Synonym: sinus lienis. Straight sinus, an unpaired dural venous sinus 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 sinus, and passes horizontally and posteriorly to the confluence of sinuses. Synonym: sinus rectus, tentorial sinus. (05 Mar 2000) |
| nerve to carotid sinus | <anatomy, nerve> A branch of the glossopharyngeal nerve that innervates the baroreceptors in the wall of the carotid sinus and the chemoreceptors in the carotid body. Synonym: ramus sinus carotici, carotid sinus branch, Hering's sinus nerve, intercarotid nerve, nerve to carotid sinus, sinus nerve of Hering. (05 Mar 2000) |
| nonphasic sinus arrhythmia | Sinus arrhythmia in which variations in rhythm are not related to the phases of respiration. (05 Mar 2000) |
| sulcus for transverse sinus | The groove on the inner surface of the occipital bone marking the course of the transverse sinus; the tentorium is attached to its margins. Synonym: sulcus sinus transversi, sulcus for transverse sinus. (05 Mar 2000) |