| nonphasic sinus arrhythmia | Sinus arrhythmia in which variations in rhythm are not related to the phases of respiration. (05 Mar 2000) |
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| 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) |
| sulcus sinus petrosi inferioris | A groove lodging the inferior petrosal sinus, formed by union of similarly named grooves in the petrous part of the temporal bone and the basilar part of the occipital bone. Synonym: sulcus sinus petrosi inferioris, inferior petrosal groove, inferior petrosal sulcus. (05 Mar 2000) |
| sulcus sinus petrosi superioris | A groove on the crest of the petrous portion of the temporal bone in which rests the superior petrosal sinus. Synonym: sulcus sinus petrosi superioris, superior petrosal sulcus. (05 Mar 2000) |
| sulcus sinus sagittalis superioris | The groove in the midline of the inner table of the calvaria lodging the superior sagittal sinus. Synonym: sulcus sinus sagittalis superioris, sagittal groove, sagittal sulcus, superior longitudinal sulcus. (05 Mar 2000) |
| sulcus sinus sigmoidei | A broad groove in the posterior cranial fossa, first situated on the lateral portion of the occipital bone, then curving around the jugular process on to the mastoid portion of the temporal bone, and finally turning sharply on the posterior inferior angle of the parietal bone and becoming continuous with the transverse groove; it lodges the transverse sinus. Synonym: sulcus sinus sigmoidei, sigmoid fossa, sigmoid groove, sigmoid sulcus. (05 Mar 2000) |
| sulcus sinus transversi | 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) |
| superior petrosal sinus | A paired dural venous sinus in the groove along the crest of the petrous temporal bone, connecting the cavernous sinus with the termination of the transverse sinus or beginning of the sigmoid sinus. Synonym: sinus petrosus superior. (05 Mar 2000) |
| superior sagittal sinus | 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) |
| dermal sinus | A sinus lined with epidermis and skin appendages extending from the skin to some deeper-lying structure, most frequently the spinal cord. (05 Mar 2000) |
| oblique pericardial sinus | 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 oesophagus. Synonym: sinus obliquus pericardii, oblique sinus of pericardium. (05 Mar 2000) |
| oblique sinus of pericardium | 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 oesophagus. Synonym: sinus obliquus pericardii, oblique sinus of pericardium. (05 Mar 2000) |
| occipital sinus | An unpaired dural venous sinus commencing at the confluence of the sinuses and passing downward in the base of the falx cerebelli to the foramen magnum. Synonym: sinus occipitalis. (05 Mar 2000) |
| opening of the sphenoidal sinus | 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) |
| tachycardia, sinus | Fast heartbeat (tachycardia) occurring because of rapid firing by the sa node, the natural pacemaker of the heart. Electrical signals initiated in the sa node are transmitted to the atria and the ventricles to stimulate heart muscle contractions heartbeats. Sinus tachycardia is usually a rapid contraction of a normal heart in response to a condition, drug, or disease. For examples, pain, fever, excessive thyroid hormone, exertion, excitement, low blood oxygen level (hypoxia), or stimulant drugs such as caffeine, cocaine, and amphetamines can cause tachycardia. However, in some cases, it can be a sign of heart failure or heart valve disease or other illness. (12 Dec 1998) |