The sigmoid sinus is a large venous channel located in the brain. It is part of the dural venous sinuses, which collect deoxygenated blood from the brain and drain it into the internal jugular vein. The sigmoid sinus has an S-shaped curve and is situated along the posterior part of the skull. This sinus plays a crucial role in the brain's venous drainage system. It receives blood from several smaller sinuses, including the transverse sinus and the cavernous sinus. Proper functioning of the sigmoid sinus is essential for maintaining healthy blood circulation in the brain.