Cerebrospinal fluid
Cerebrospinal fluid (CSF), clear, colorless liquid that fills and surrounds the brain and the spinal cord and provides a mechanical barrier against shock.
- Total amount: There are roughly 100β150 ml of CSF in the adult human body.
- Production rate: About 430β530 mL of CSF are produced each day.
- Turnover: The full volume of CSF is replaced between three and four times each day.
- Location: Ventricles in the brain house 25 to 35 mL of CSF; the remainder is contained in the subarachnoid space and spinal canal.
- Composition: CSF is 99 percent water and 1 percent solutes, such as ions, glucose, and neurotransmitters.
Cerebrospinal fluid (CSF) is slightly alkaline and consists of about 99 percent water and 1 percent various solutes, including glucose, ions, neurotransmitters, and proteins. It is formed primarily in the ventricles of the brain by the choroid plexus, a capillary network covered in a thin layer of epithelial cells. The fluid is produced as the epithelial cells actively transport sodium ions into the ventricles; these ions are followed by chlorine, which generates an osmotic gradient that then pulls water into the ventricles.
CFS is eventually absorbed into the veins; it leaves the cerebrospinal spaces in a variety of locations, including spaces around the spinal roots and the cranial nerves. Movement of the CSF is affected by the downward pull of gravity, the continual process of secretion and absorption, blood pulsations in contingent tissue, respiration, pressure from the veins, and head and body movements. In total, there are about 100 to 150 ml of CSF in the adult human body, and it is continually produced, being fully replaced every six to eight hours.
CSF acts primarily to support the brain and to provide lubrication between surrounding bones and the brain and spinal cord. When an individual suffers a head injury, the fluid acts as a cushion, dulling the force by distributing its impact. The fluid also helps to maintain pressure within the cranium at a constant level. An increase in the volume of blood or brain tissue results in a corresponding decrease in the fluid. Conversely, if there is a decrease in the volume of matter within the cranium, as occurs in atrophy of the brain, the CSF compensates with an increase in volume. The fluid also transports metabolic waste products, antibodies, chemicals, and pathological products of disease away from the brain and spinal-cord tissue into the bloodstream.
Examination of the CSF may diagnose a number of diseases. A fluid sample is obtained by inserting a needle into the lumbar region of the lower back below the termination of the spinal cord; this procedure is called a lumbar puncture (or spinal tap). If the CSF is cloudy, meningitis (inflammation of the central nervous system lining) may be present. Blood in the fluid may indicate a hemorrhage in or around the brain.