cerebrospinal fluid

a clear, colourless fluid with a similar composition to LYMPH . It fills the ventricles and cavities in the CENTRAL NERVOUS SYSTEM and bathes all the surfaces of the brain and spinal cord. The brain floats in it, and it has a protective function, acting as a shock absorber and helping to prevent mechanical injury to the central nervous system. The cerebrospinal fluid is secreted by the CHOROID PLEXUSES in the ventricles of the brain, and it contains some white blood cells (but no red), salts, glucose and enzymes. It is reabsorbed by veins back into the bloodstream.