CSF is produced by choroid plexus. It starts flowing from the lateral ventricles and move towards the fourth ventricle via the third ventricle. It then moves towards the subarachnoid space which is the region surrounding the brain and spinal cord. From the brain and spinal cord, CSF is absorbed through the blood vessels and passed into the bloodstream again. It then moves to the kidney and liver for filtration.
Explanation: in able to do this it has to transport proteins that can span the cell membrane and allowi the permeable membrane to regulate which molecules enter and leave a cell.
