ABSTRACT
The composition of CSF is similar but not identical to that o f plasma. C SF is formed by a combination o f processes that include passive diffusion, facilitated diffu sion, and active transport. I t is produced primarily, but not exclusively, by the choroid plexus o f the ventricular system. T he CSF circulates through the ventricular sys tem into the subarachnoid space and over the surface o f the brain and spinal cord. M ost of the CSF passes through the arachnoid villi into the venous sinuses.
