Which structure primarily reabsorbs CSF into the venous circulation?

Which structure primarily reabsorbs CSF into the venous circulation?

• A. Choroid plexus
• B. Arachnoid villi
• C. Pia mater
• D. Subarachnoid granulations.

Answer: (B)

CSF reabsorption into the bloodstream occurs mainly through arachnoid villi (arachnoid granulations) that protrude into the dural venous sinuses, especially the superior sagittal sinus. These structures act as one-way channels driven by pressure differences, allowing CSF to move into venous blood when CSF pressure exceeds venous pressure, thereby regulating CSF volume and pressure. The choroid plexus is where CSF is produced, not reabsorbed, so it’s not the correct route. The pia mater is a thin inner meningeal layer and is not involved in CSF reabsorption. Subarachnoid granulations are often used interchangeably with arachnoid villi, but the key site for reabsorption into the venous system is the arachnoid villi.

CSF reabsorption into the bloodstream occurs mainly through arachnoid villi (arachnoid granulations) that protrude into the dural venous sinuses, especially the superior sagittal sinus. These structures act as one-way channels driven by pressure differences, allowing CSF to move into venous blood when CSF pressure exceeds venous pressure, thereby regulating CSF volume and pressure.

The choroid plexus is where CSF is produced, not reabsorbed, so it’s not the correct route. The pia mater is a thin inner meningeal layer and is not involved in CSF reabsorption. Subarachnoid granulations are often used interchangeably with arachnoid villi, but the key site for reabsorption into the venous system is the arachnoid villi.