True statement about cerebrospinal fluid is

Ref:1. Koeppen BM, Stanton BA. The Nervous System: Introduction to Cells and Systems. In: Berne & Levy Physiology 6th ed. Mosby; 2008 p 61-62.2. W F Ganong. Excitable Tissue: Nerve. In: Review of Medical Physiology. 21st ed. California: McGraw-Hill Companies; 2003Explanation:Cerebrospinal Fluid50-70% of the CSF is formed in the choroid plexuses and the remainder is formed around blood vessels and along ventricular wallsAbout two thirds or more of this fluid originates as secretion from the choroid plexuses in the four ventricles, mainly in the two lateral ventriclesTwo lateral ventricles communicate with the third ventricle through two independent openings, foramina of monro'From the third ventricle, CSF flows downward along the aqueduct of Sylvius into the fourth ventricleAfter it leaves the ventricular system. CSF circulates through the subarachnoid space that surrounds the brain and spinal cord.The volume of CSF within the cerebral ventricles is approximately 30 mL. and that in the subarachnoid space is about 125 mLLumbar CSF pressure is normally 70 to 180 mm H2O.The rate of CSF formation is independent of intraventricular pressure. However, absorption is proportional to the pressureAt a pressure of 112 mm H2O. filtration and absorption are equal.Below 68 mm H2O. absorption stops