| MS | Maffuci syndrome; maladjustment score; mandibular series; Marfan syndrome; Marie-Strumpell [syndrome... |
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| RMS | rectal morphine sulfate [suppository]; red man syndrome; repetitive motion syndrome; respiratory mus... |
| SD | Sandhoff disease; senile dementia; septal defect; serologically defined; serologically detectable; s... |
| US | screen unsharpness ultrasonic, ultrasound; ultrasonography; unconditioned stimulus; unique sequence;... |
| UTS | Ullrich-Turner syndrome; ulnar tunnel syndrome; ultimate tensile strength |
| sinus aortae | 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. Synonym: sinus aortae, Petit's sinus, Valsalva's sinus. Arlt's sinus, an inconstant depression on the lower portion of the internal surface of the lacrimal sac. Barber's pilonidal sinus, pilonidal sinus 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. (05 Mar 2000) |
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| sinus arrest | <cardiology, physiology> Cessation of sinus activity; the ventricles may continue to beat under ectopic atrial, atrioventricular junctional, or idioventricular control. See: sinus standstill, atrial standstill. (05 Mar 2000) |
| sinus arrhythmia | <cardiology, physiology> An increase in heart rate during inspiration. A normal physiologic response, more pronounced in children. (27 Sep 1997) |
| sinus barotrauma | Sinus troubles, particulaqrly with pain, due to changing atmospheric pressures, as when going up or down in a plane. Also called aerosinusitis or barosinusitis. (12 Dec 1998) |
| sinus bradycardia | <cardiology, physiology> Bradycardia originating in the normal sinus pacemaker. (05 Mar 2000) |
| 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) |
| 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) |