cerebrospinal fluid

Clear fluid that buffers the brain and spinal cord. It is present in the subarachnoid space, the four ventricles of the brain and the central canal of the spinal cord. It is secreted in clusters of blood vessels in the ventricles known as choroid plexuses, and is eventually absorbed into the bloodstream. Its normal contents include glucose, salts, proteins and some white cells. Small amounts of CSF may be withdrawn by lumbar puncture for diagnostic tests.