CSF circulates through the brain and spinal cord and is reabsorbed into the venous circulation. Through which structures does this reabsorption primarily occur?

• A. Arachnoid granulations
• B. Dural venous sinuses
• C. Central canal
• D. Choroid plexus

Answer: (A)

CSF reabsorption into the venous system happens mainly through arachnoid granulations. These are small villous projections of the arachnoid mater that extend into the dural venous sinuses, especially the superior sagittal sinus. CSF in the subarachnoid space flows through these granulations into the bloodstream when the pressure in the CSF exceeds venous pressure, acting as one-way valves into the venous system. The choroid plexus is where CSF is produced, not reabsorbed, while the central canal is merely part of the spinal cord’s ventricular system and not a route for CSF reabsorption. Dural venous sinuses are the destination for CSF after it passes the granulations, not the primary site of reabsorption themselves.