The sigmoid sinus is a large venous channel located in the brain. It is part of the dural venous sinuses, which are spaces that collect blood from the brain and direct it back to the heart. The sigmoid sinus runs along the inner surface of the skull and eventually drains into the internal jugular vein. This sinus plays a crucial role in the brain's venous drainage system. It receives blood from various sources, including the cerebral veins and the transverse sinus. Proper functioning of the sigmoid sinus is essential for maintaining healthy blood flow and pressure within the cranial cavity.