si'nus

PI. sinuses. 1. A cavity having a relatively narrow opening or entrance. 2. A large venous canal into which several smaller veins empty, especially such a venous channel formed by the dura of the brain. 3. The bosom. 4. The long narrow suppurating tract communicating with an absce or diseased ti ue, acce ory s'es, air s'es. Air-containing cavities within bones, especially those communicating with the nasal pa ages, aortic s. See s'es of Valsalva, basilar s. See transverse s. Breschet's s. See Breschet. cavernous s. A large s. extending from the sphenoidal fi ure to the apex of the petrous portion of the temporal bone, communicating behind with the inferior and superior petrosal s'es, and receiving the ophthalmic vein in front, circular s.. Syn.: communicatio recept a culorimi. A venous s. surrounding the pituitary body, communicating on each side with the cavernous s. circular s. of the placenta. A plexus of veins in the maternal portion of the placenta in communication circular with uteroplacental s'es. clinoid s. See s. confluence of the s'es. See torcular Hero phil i, under torcular. coronary s. of the heart. A vein in the transverse groove between the left auricle and ventricle of the heart on its posterior aspect; by some regarded as a dilatation of the great cardiac vein or a s. into which it opens, cranial s'es. Venous channels between the folds of the dura, lined with a continuation of the tunica intern a of the veins, ethmoidal s'es. See ethmoidal cells, under cells, frontal s. An irregular cavity in the frontal bone, underlying the prominence at the root of the nose and over the superior orbital margin, extending upward and outward between the two tables of the bone, separated from its fellow of the opposite side by a thin septum, and communicating with the nose by the infundibulum. genital s. The cleft of the vulva, genitourinary s. See urogenital s. great s.