Final answer:
CSF is produced by the choroid plexus, flows from the ventricles into the subarachnoid space, provides protection and waste removal for the CNS, and is reabsorbed into the bloodstream through arachnoid granulations.
Step-by-step explanation:
The subarachnoid space receives cerebrospinal fluid (CSF) from the choroid plexus located in the four ventricles of the brain. This special fluid is essential for providing a liquid cushion, protecting the brain and spinal cord, and helping to remove metabolic wastes from the central nervous system (CNS). Specifically, CSF production occurs at a rate of 500 ml/day by modified ependymal cells in the choroid plexuses, and because the brain can accommodate only 135-150 ml, the excess fluid must be properly drained.
CSF circulation begins when the fluid is produced in the ventricles and then moves through the median and lateral apertures, eventually entering the subarachnoid space. It bathes the CNS, and its continuous flow is critical for diluting potentially harmful substances. Eventually, the CSF is reabsorbed back into the bloodstream through the arachnoid granulations in the superior sagittal sinus. These outpocketings of the arachnoid membrane allow CSF to move from the subarachnoid space into the dural sinuses, and then into the venous system to be reoxygenated and filtered by the body's organs.