| sinus caroticus | <anatomy> A slight dilation in the carotid artery at its bifurcation into the external and internal carotid arteries, it contains baroreceptors (pressure sensors) that when stimulated, will cause a reflex slowing of the heart, vasodilation and a fall in blood pressure. (27 Sep 1997) |
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| sinus cavernosus | <radiology> Contents: III oculomotor n., IV trochlear n., V-1 ophthalmic n. (trigeminal n.), V-2 maxillary n. (trigeminal n.), VI abducens n. Note: mandibular n. (V-3) passes through foramen rotundum (12 Dec 1998) |
| sinus circularis | sinus venosus sclerae |
| sinus coronarius | 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. Synonym: sinus coronarius. (05 Mar 2000) |
| sinus durae matris | Endothelium-lined venous channels in the dura mater. Synonym: sinus durae matris, cerebral sinuses, cranial sinuses, sinuses of dura mater, venous sinuses. (05 Mar 2000) |
| sinus epididymidis | A narrow space between the body of the epididymis and the testis. Synonym: sinus epididymidis. Ethmoidal sinuses, ethmoidal air-cells; evaginations of the mucous membrane of the middle and superior meatuses of the nasal cavity into the ethmoidal labyrinth forming multiple small paranasal sinuses; they are subdivided into anterior, middle and posterior ethmoidal sinuses. Synonym: antra ethmoidalia. (05 Mar 2000) |
| sinus ethmoidales | The numerous small air-filled cells of the ethmoidal labyrinth. See: anterior ethmoidal air cells, middle ethmoidal air cells, posterior ethmoidal air cells. Synonym: cellulae ethmoidales, sinus ethmoidales, ethmoidal cells. (05 Mar 2000) |
| sinus ethmoidales anteriores | The anterior group of air cells of the ethmoidal sinus's; each sinus communicates with the middle meatus of the nasal cavity. Synonym: sinus ethmoidales anteriores, anterior cells, anterior sinuses, cellulae anteriores. (05 Mar 2000) |
| sinus ethmoidales mediae | The middle group of air cells of the ethmoidal sinus's; each sinus communicates with the middle meatus of the nasal cavity. Synonym: sinus ethmoidales mediae, cellulae mediae, middle cells, middle ethmoidal sinuses. (05 Mar 2000) |
| sinus ethmoidales posteriores | The posterior group of air cells of the ethmoidal sinus's; each sinus communicates with the superior meatus of the nasal cavity. Synonym: sinus ethmoidales posteriores, cellulae posteriores, posterior cells. (05 Mar 2000) |
| sinus frontalis | One of the paired, but seldom symmetrical, air spaces located between the inner and outer compact layers of the frontal bone. (12 Dec 1998) |
| sinus histiocytosis | A condition marked by the abnormal appearance of histiocytes (macrophages) in the blood. Lipid h., Niemann-Pick disease. Sinus h., a disorder of the lymph nodes in which the distended sinuses are completely or nearly completely, filled by histiocytes, as a result of active multiplication of the littoral cells. H. X, a generic term embracing eosinophilic granuloma, Letterer-Siwe disease and Hand-Schuller-Christian disease and indicating a shared common origin for the three entities. (16 Dec 1997) |
| sinus histiocytosis with massive lymphadenopathy | A chronic disease occurring in children and characterised by massive painless cervical lymphadenopathy due to distension of the lymphatic sinuses by macrophages containing ingested lymphocytes, and by capsular and pericapsular fibrosis. Synonym: Rosai-Dorman disease. (05 Mar 2000) |
| sinus intercavernosi | The anterior and posterior anastomoses between the cavernous sinus's, passing anterior and posterior to the hypophysis and forming, with the cavernous sinuses, the circular sinus. Synonym: sinus intercavernosi, Ridley's sinus. Jugular sinus Sinus jugularis, one of three enlargements of the jugular veins; the external jugular sinus is between the two sets of valves; the internal jugular sinus's are at the origin (superior bulb) and near the termination (inferior bulb). (05 Mar 2000) |
| sinus lactiferi | A circumscribed spindle-shaped dilation of the lactiferous duct just before it enters the nipple. In nursing mothers this dilatation stores a droplet of milk which is expressed by compression as the infant begins to suckle; this is thought to encourage continual suckling while the let-down reflex ensues. Synonym: sinus lactiferi, ampulla lactifera, ampulla of milk duct, lactiferous ampulla. (05 Mar 2000) |