The choroid plexus mediates the production of cerebrospinal fluid (CSF). CSF acts as a medium for filtration system that facilitates the removal of metabolic waste from the brain and exchange of biomolecules and xenobiotics into and out of the brain.[5][6][3] In this way the choroid plexus has a very important role in helping to maintain the delicate extracellular environment required by the brain to function optimally.