| sigmoid sinus | The S-shaped dural venous sinus lying deep to the mastoid process of the temporal bone and immediately posterior to the petrous temporal bone; it is continuous with the transverse sinus and empties into the internal jugular vein as it passes through the jugular foramen. Synonym: sinus sigmoideus. (05 Mar 2000) |
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| sigmoid sulcus | 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) |
| sigmoid veins | The several tributaries of the inferior mesenteric vein that drain the sigmoid colon. Synonym: venae sigmoideae. (05 Mar 2000) |
| sigmoid volvulus | Relatively common location of volvulus, with obstruction either proximal or distal to the sigmoid segment. (05 Mar 2000) |