ABSTRACT
Humans produce approximately 0.3 ml of CSF per minute, corresponding to 400-500 ml per day for the average adult. CSF arises from modified ependymal cells of the choroid plexus, a highly vascular structure within the lateral, third and fourth ventricles. Modest amounts of CSF are also produced by the ependymal cells that line the ventricular system within the brain. CSF largely represents an ultrafiltrate of blood; each cardiac systole facilitates CSF production, whereas each diastole allows resorption of CSF into the systemic circulation. Certain
components of CSF, such as glucose and protein, enter the CSF via facilitated or active transport, as discussed further below. The intracranial volume of CSF in adults averages approximately 75 ml; the volume in all CSF spaces is approximately 150 ml in adults. By contrast, the total CSF volume in young infants is only 30-50 ml.
