Cerebrospinal Fluid: The Support Of Our Central Nervous System
Cerebrospinal fluid (CSF) or cerebrospinal fluid is one of the main fluids in the human body. Its main function is to protect brain tissue and the spinal cord. It acts as a shock absorber against impacts between the central nervous system and the surrounding skull or bones. Under normal conditions, the CSF has a volume of between 100 and 150 ml.
It is transparent, its chemical content is different from that of serum, but similar to that of blood plasma. It has the same consistency as water and is essentially composed of H2O, minerals (sodium, potassium, calcium, chlorine), inorganic salts (phosphates) and vitamins (especially of group B). It also contains electrolytes, leukocytes, amino acids, choline, and nucleic acid, among other components.
A type of extracellular fluid
The body has 4 fluid compartments, which are divided into intra and extracellular. Almost two-thirds of the total water in our organism is intracellular or intravascular fluids. In other words, the liquid part of the cytoplasm of cells. The rest is extracellular. There were 3 fluids of the latter type.
- Blood plasma, in other words, the liquid part of the blood; which is contained in the blood vessels and in the heart chambers.
- The interstitial, also called tissue, which is in the interstice or space between cells.
- And, third, the cerebrospinal fluid or cerebrospinal fluid, which bathes the brain and spinal cord. We will explore its composition, location and functions in more detail below.
Location and traffic
CSF circulates through the subarachnoid space, the ventricles of the brain, and the ependymal duct. Let’s see this by part:
- The subarachnoid space is that which exists between the intermediate meninge (arachnoid) and the internal meninge (pia mater). The pia mater is in contact with the surface of the brain, so that by this small space through which cerebrospinal fluid circulates separates the skull from the brain.
- The cerebral ventricles: these are four anatomical chambers located in the brain, which are interconnected with each other. Together, they form the ventricular system through which CSF circulates.
- The ependymal canal: this is a duct that crosses the entire spinal cord. It contains over 140ml of cerebrospinal fluid from the body of an average individual. It occupies the center of the spinal cord, being located in the center of the gray commissure and dividing it into an anterior part and a posterior part.
Synthesis and course of cerebrospinal fluid
Most of the cerebrospinal fluid is created from the blood plasma in the choroid plexuses of the ventricles of the brain. Once synthesized, it passes to the lateral ventricles, located in both cerebral hemispheres. And, later, through the interventricular holes, to the third ventricle (located at the level of the diencephalon).
It runs along the Sylvian aqueduct and stops in the fourth ventricle, which is triangular in shape and is in the hindbrain, very close to the brainstem and cerebellum. Once this course is completed, it enters the subarachnoid space through holes known as Magendie and Luschka, and bathes the entire surface of the central nervous system.
Finally, it is reabsorbed in the venous sinuses in a passive process for which no energy is required. Under normal conditions, CSF is absorbed very quickly, almost at the same rate that it is formed in the choroid plexus, so that intracranial pressure remains constant.
Cerebrospinal fluid is renewed about 6-7 times a day, and its average life cycle usually does not exceed 3 hours. When the circulation routes of cerebrospinal fluid are blocked and the latter accumulates in certain brain compartments, then hydrocephalus occurs. The immediate consequence is an increase in intracranial pressure.
Functions of cerebrospinal fluid
The cerebrospinal fluid, bodily fluid of our organism, has very varied functions.
- CSF protects the central nervous system against possible trauma, shock and impact. We can say that it is able to dampen intracranial movement up to 97%.
- It assumes a dual biological function. On the one hand, nutrition. It is responsible for the transport of hormones, antibodies, lymphocytes to nervous tissues. On the other hand, elimination. It rejects neuronal metabolic residues.
- In addition, it acts as an electrical insulator of the spinal cord.
- It makes it possible to diagnose a series of neurological diseases, alterations of the meninges, subarachnoid hemorrhages or cerebrospinal tumors.
- This is the gateway to epidural anesthesia.
CSF is, as we see, essential for the maintenance and preservation of the central nervous system. Small changes in their density or quantity can therefore have serious consequences on the functioning of the brain.
Bibliographical references
Zweckberger K, Sakowitz OW, Unterberg AW, et al. (2009). Intracranial pressure-volume relationship. Physiology and pathophysiology Anaesthesist. 58: 392-7.
Our thoughts The puzzles of the human brain are a permanent source of research that science has not yet been able to answer.
