| sinus phlebitis | Inflammation of a cerebral sinus. (05 Mar 2000) |
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| sinus pocularis | A minute pouch in the prostate opening on the summit of the seminal colliculus, the analogue of the uterus and vagina in the female, being the remains of the fused caudal ends of the paramesonephric ducts. Synonym: utriculus prostaticus, masculine uterus, Morgagni's sinus, sinus pocularis, uterus masculinus, vagina masculina, vesica prostatica, Weber's organ. (05 Mar 2000) |
| sinus posterior | A deep groove above the pyramidal eminence extending to the incudal fossa in the posterior wall of the tympanic cavity. (05 Mar 2000) |
| sinus prostaticus | The groove on either side of the urethral crest in the prostatic part of the urethra into which the prostatic ducts open. Synonym: sinus prostaticus. (05 Mar 2000) |
| sinus rectus | straight sinus |
| sinus reflex | See: carotid sinus syndrome. (05 Mar 2000) |
| sinus renalis | The cavity of the kidney, containing the calyces 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. Synonym: sinus renalis. (05 Mar 2000) |
| sinus reuniens | An obsolete term for sinus venosus. Rhomboidal sinus Sinus rhomboidalis, a dilation of the central canal of the spinal cord in the lumbar region. Synonym: rhombocele. (05 Mar 2000) |
| sinus rhythm | The normal regular cardiac rhythm stimulated by the sinoatrial node. (27 Sep 1997) |
| sinus sagittalis inferior | An unpaired dural venous sinus in the lower margin of the falx cerebri, running parallel to the superior sagittal sinus and merging with the great cerebral vein to form the the straight sinus. Synonym: sinus sagittalis inferior, inferior longitudinal sinus. (05 Mar 2000) |
| sinus sagittalis superior | An unpaired dural venous sinus in the sagittal groove, beginning at the foramen caecum and terminating at the confluence of sinuses where it merges with the straight sinus; receives the superior cerebral veins and has lateral extensions, the lateral venous lacunae. Synonym: sinus sagittalis superior, superior longitudinal sinus. Tarsal sinus, a hollow or canal formed by the groove of the talus and the interosseous groove of the calcaneus which is occupied by the interosseous talocalcaneal ligament. Synonym: sinus tarsi, tarsal canal. (05 Mar 2000) |
| sinus septum | A small fold forming the medial end of the valve of the inferior vena cava; it is developed from the dorsal wall of the embryonic sinus venosus. (05 Mar 2000) |
| sinus sigmoideus | The S-shaped dural venous sinus lying deep to the mastoid process of the temporal bone and immediately posterior to the petrous temporal bone; it is continuous with the transverse sinus and empties into the internal jugular vein as it passes through the jugular foramen. Synonym: sinus sigmoideus. (05 Mar 2000) |
| sinus sphenoidalis | 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) |
| sinus sphenoparietalis | 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) |