| Ridley's sinus | 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) |
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| groove for inferior petrosal sinus | 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) |
| groove for sigmoid sinus | 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) |
| groove for superior petrosal sinus | 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) |
| groove for superior sagittal sinus | 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) |
| groove 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) |
| Petit's sinus | 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) |
| Guerin's sinus | A cul-de-sac or diverticulum behind the valve of the navicular fossa. (05 Mar 2000) |
| petrosal sinus | See: inferior petrosal sinus, superior petrosal sinus. (05 Mar 2000) |
| petrosal sinus sampling | Sampling of blood levels of the adrenocorticotropic hormone (acth) by withdrawal of blood from the inferior petrosal sinus. The inferior petrosal sinus arises from the cavernous sinus and runs to the internal jugular vein. Sampling of blood at this level is a valuable tool in the differential diagnosis of cushing disease, cushing syndrome, and other adrenocortical diseases. (12 Dec 1998) |
| phasic sinus arrhythmia | Sinus arrhythmia in which the irregularity is related to the phases of respiration, the rate being faster in inspiration and slower in expiration. (05 Mar 2000) |
| circular sinus | Dural venous formation which surrounds the hypophysis, composed of right and left cavernous sinuses and the intercavernous sinuses. Synonym: circulus venosus ridleyi, Ridley's circle. A venous sinus at the periphery of the placenta. Synonym: sinus venosus sclerae. (05 Mar 2000) |
| phrenicocostal sinus | The cleftlike extension of the pleural cavity between the diaphragm and the rib cage; pleural effusions collect here when in the upright position, and since the lung only partially enters, this is the site of thoracocentesis. Synonym: recessus costodiaphragmaticus, phrenicocostal sinus. (05 Mar 2000) |
| coccygeal sinus | A fistula opening in the region of the coccyx, being the result of incomplete closure of the caudal end of the neurenteric canal. See: pilonidal sinus. (05 Mar 2000) |
| pilonidal sinus | A dimple in the crease between the buttocks. (12 Dec 1998) |