Cerebrospinal Fluid
Anatomy and Physiology
Cerebrospinal fluid (CSF) is a clear, colorless body fluid found in the brain and spinal cord. It is produced by specialized ependymal cells in the choroid plexus of the ventricles of the brain, and absorbed in the arachnoid granulations.
CSF has three main functions: to protect the brain tissue from injury, to supply nutrients to the nervous system tissue, and to carry waste away from the surrounding tissues. The CSF circulates in the subarachnoid space (between the arachnoid mater and the pia mater) and the ventricular system around and inside the brain and spinal cord.
Production and Absorption
The CSF is produced at a rate of 500 ml per day. While it circulates, the CSF flows through the ventricles by the pulsations of the choroid plexus and by the motion of the cilia of ependymal cells. Once the CSF has completed its circulation, it is absorbed into the bloodstream through arachnoid granulations, which extend into the superior sagittal sinus.
Composition
The CSF is primarily water, with a slight presence of electrolytes, glucose, and proteins. The concentrations of these substances can change dramatically in response to the metabolic needs of the brain, trauma, disease, or drug exposure. The CSF also contains few cells, mostly lymphocytes.
Clinical Significance
Abnormalities in the CSF can indicate a variety of conditions. For instance, an increase in intracranial pressure can indicate conditions such as hydrocephalus or brain tumor. Changes in the composition of the CSF can also indicate diseases such as meningitis or multiple sclerosis. Lumbar puncture (spinal tap) is a common procedure to collect a sample of CSF for analysis.
