Where does the sigmoid sinus drain?

The sigmoid sinus plays a crucial role in venous drainage from the brain. It is a large venous channel located within the posterior cranial fossa, and it is the continuation of the transverse sinus. The primary function of the sigmoid sinus is to collect blood from the brain's venous system and transport it away from the cranial cavity.

This sinus drains specifically into the internal jugular vein, which is the major vein responsible for returning deoxygenated blood from the head and neck back to the heart. The internal jugular vein then joins with the subclavian vein to form the brachiocephalic vein, which subsequently drains into the superior vena cava.

Understanding the drainage pathway of the sigmoid sinus is essential because it highlights the importance of this structure in maintaining proper venous circulation from the brain. The anatomy of this drainage route clarifies how blood from the brain, after filtering through various smaller venous structures, ultimately reaches the heart. This is vital for the removal of metabolic waste from the brain and ensuring adequate blood supply to maintain neuronal function.

Given this anatomical relationship, the choice indicating that the sigmoid sinus drains into the internal jugular vein is accurate and reflects the correct physiological understanding of cranial venous drainage.