The sigmoid sinuses (left & right), within the human head, are two areas beneath the brain which allow blood to drain inferiorly from the posterior center of the head. They drain from the transverse sinuses (under the back of the brain) and converge with the inferior petrosal sinuses to form the internal jugular vein. See diagram (at right): labeled under the brain as "PARS SIGMOID." (for Latin: sigmoideus).
Each sigmoid sinus begins beneath the temporal bone and follows a tortuous course to the jugular foramen, at which point the sinus becomes continuous with the internal jugular vein.
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