CSF absorption into the venous system occurs via which structures?

CSF absorption into the venous system occurs via which structures?

• A. Arachnoid villi
• B. Choroid plexus
• C. Blood-brain barrier
• D. Dural venous sinuses without villi

Answer: (A)

CSF absorption into the venous system occurs mainly through arachnoid villi, tiny projections of the arachnoid membrane that extend into the dural venous sinuses. These structures act as one-way outlets: when the CSF pressure in the subarachnoid space is higher than venous pressure, CSF is pressed through the villi into the venous blood, helping to maintain normal CSF volume and pressure. The choroid plexus is where CSF is produced, not absorbed, so it doesn’t serve as the drainage pathway. The blood-brain barrier is a restrictive interface at CNS capillaries, not a route for CSF to enter the venous system. Dural venous sinuses without villi wouldn’t effectively absorb CSF because the essential transfer mechanism requires those villous structures. Impaired absorption via arachnoid villi can lead to hydrocephalus due to CSF accumulation.

CSF absorption into the venous system occurs mainly through arachnoid villi, tiny projections of the arachnoid membrane that extend into the dural venous sinuses. These structures act as one-way outlets: when the CSF pressure in the subarachnoid space is higher than venous pressure, CSF is pressed through the villi into the venous blood, helping to maintain normal CSF volume and pressure.

The choroid plexus is where CSF is produced, not absorbed, so it doesn’t serve as the drainage pathway. The blood-brain barrier is a restrictive interface at CNS capillaries, not a route for CSF to enter the venous system. Dural venous sinuses without villi wouldn’t effectively absorb CSF because the essential transfer mechanism requires those villous structures. Impaired absorption via arachnoid villi can lead to hydrocephalus due to CSF accumulation.