Venous sinuses are large channels within the brain that collect deoxygenated blood from the cerebral veins. They are part of the venous system and help drain blood away from the brain, directing it toward the internal jugular veins. These sinuses are located between layers of the dura mater, which is the outermost membrane covering the brain. They play a crucial role in maintaining proper blood flow and pressure within the cranial cavity, ensuring that waste products are efficiently removed from the brain's circulation.