The entire central nervous system contains between 3 to 5 ounces (80 to 150 milliliters) of cerebrospinal fluid, a clear, colorless liquid. The choroid plexus produces nearly 17 ounces (500 milliliters) of cerebrospinal fluid per day, effectively replacing the cerebrospinal fluid every eight hours (three times per day). Normally, cerebrospinal fluid flows through the ventricles, exits into cisterns (closed spaces that serve as reservoirs) at the base of the brain, bathes the surfaces of the brain and spinal cord, and then is absorbed into the bloodstream.