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Cerebrospinal fluid: composition, functions and disorders

Cerebrospinal fluid: composition, functions and disorders

July 18, 2024

It is popular knowledge that the brain is located inside the skull, being protected among other things by this and by different membranes, such as the meninges.

The correct functioning and protection of this organ is fundamental for survival , so that it is necessary to nourish it and avoid possible damages, such as those produced by blows or intracranial pressure. Furthermore, in its necessarily continuous operation waste is generated, which can be harmful and therefore must be removed from the system.

In all this, there is a very important liquid that circulates through the nervous system, known as cerebrospinal fluid .

A general idea of ​​cerebrospinal fluid

Cerebrospinal fluid or cerebrospinal fluid is a substance present in the nervous system, both at the level of the brain and the spinal cord , which performs various functions such as protection, maintenance of intracranial pressure and health status of the thinking organ.

Its presence in the nervous system occurs especially in the subarachnoid space (between the arachnoid and the pia mater, two of the meninges that protect the brain) and the cerebral ventricles. It is a transparent liquid of fundamental importance in the preservation and good health of the brain, with a composition similar to that of blood plasma, from which it is derived. Despite being colorless, different alterations and infections can give it different shades, its color being a sign of the presence of a problem.

Life cycle of cerebrospinal fluid

Cerebrospinal fluid is synthesized in the choroid plexuses, small structures present in the lateral ventricles, being the main function of these plexuses the production of this substance. This production is given continuously, renewed to maintain a constant amount of said substance .

Once emitted it flows from the lateral ventricles to the third ventricle and later to fourth through the aqueduct of Silvio. From there it ends up projecting into the subarachnoid space through an orifice known as the Magendie orifice and the Luschka orifices, openings in the fourth cerebral ventricle that contact the ventricular and meningeal systems when communicating with the cistern of the subarachnoid space ( located between the arachnoid meninges and pia mater). From that point circulates through the meninges throughout the entire nervous system, exercising various functions in the process.

To culminate with its life cycle, it is finally reabsorbed through the arachnoid granulations, which connect with the veins present in the dura, with which the liquid ends up reaching the bloodstream.

The average life cycle of this substance is around three hours , between its secretion, circulation, collection and renewal.


As just mentioned, the composition of the cerebrospinal fluid is very similar to that of blood plasma , the main variations being the comparatively much lower presence of proteins (it is estimated that in the blood plasma the presence of proteins is two hundred times greater) and the type of electrolytes that are part of it.

A water-based solution, cerebrospinal fluid has several components of great importance for the maintenance of the nervous system, such as vitamins (especially group B), electrolytes, leukocytes, amino acids, choline and nucleic acid.

Within this large number of elements, cerebrospinal fluid highlights the presence of albumin as the main protein component , along with others such as prealbumin, alpha-2-macroglobulin or transferrin. Apart from these components, the high presence of glucose stands out, having between 50 and 80% of presence in this solution, which is so vital for the encephalon.

Principal functions

We have visualized an optics of what is the cerebrospinal fluid, where it circulates and what it is composed of. But nevertheless One wonders why this substance is so important for the correct functioning of the whole nervous system. To answer this question it is necessary to see what functions it has.

One of the main functions of cerebrospinal fluid is to be the main mechanism for the elimination of waste produced by the continuous functioning of the nervous system , waste that could seriously affect its operation. Thus, the circulation of cerebrospinal fluid takes those substances and metabolites, which will end up being excreted from the system.If this substance does not exist, the remaining toxins and particles would remain deposited in regions of the nervous system and adjacent areas, so that many problems would appear in the state of living cells: neither could they get rid of those leftover elements, nor could they access to the parts of these that can be recycled once they have passed through the right place.

Another of the most important functions of the cerebrospinal fluid is to keep the brain nourished, as well as to ensure the consistency of the medium between the different cells of the brain and the medulla. It is a kind of chemical "shock absorber" that allows the room for maneuver to increase in case of certain hormonal imbalances, for example, and when there are problems of homeostasis in general .

Cerebrospinal fluid also allows the brain to remain floating in the skull, greatly reducing its weight. This flotation also serves as a buffer against aggressions, blows and movements by reducing the possibility of collision with the bones of the skull or external elements.

Also, the cerebrospinal fluid it has a lot to do with maintaining intracranial pressure , making it neither too big nor too small, maintaining a constant balance that allows correct operation.

Finally, it also participates by acting as an immune system, protecting the nervous system from harmful agents. It also contributes as a means of transporting hormones.

Derived disorders

Thus, the nervous system has an essential tool in the cerebrospinal fluid to function correctly.

But nevertheless, It is possible that there are alterations in the synthesis, circulation or resorption of this substance , which can cause different problems, two of which are the following.

1. Hydrocephalus

This concept refers to the excessive presence of cerebrospinal fluid , having such an accumulation that causes a pressure of the brain against the skull. Some of the elements that can cause it are tumors, infections or traumatisms, but it is also common to find congenital hydrocephalus, that is, present from birth.

It can cause from headache, vomiting, cognitive or coordination impairment or double vision, among other symptoms, being in the case of congenital hydrocephalus cause of a strong difficulty in the development and intellectual deficit. It is usually due to obstructions in the circuit, being a common example that Magendie's hole is blocked. To treat these problems it is possible to perform surgery in order to place an escape route of the liquid to other areas, such as the stomach.

2. Hypertension / intracranial hypotension

An excess or deficit of cerebrospinal fluid can cause the pressure suffered by the brain inside the skull to be excessive or too low to allow proper functioning. While hypotension would occur to the loss or little production of cerebrospinal fluid, hypertension would be caused by an excess of this, which can be serious because it presses areas of the nervous system and prevents them from working well (or even kills areas of cell tissue ).

In any case, the alterations in the cerebrospinal fluid that may appear in these cases add to the problems of the heart condition that originates , so that the danger increases. It is necessary to treat both groups of symptoms to avoid a chain effect resulting from problems in the functioning of the nervous system and the circulatory system.

Bibliographic references:

  • Rodríguez-Segade, S. (2006). Cerebrospinal fluid. Ed Cont Lab Clin.; 9: 49-56.
  • Rosenberg, G.A. (2008). Brain edema and disorders of cerebrospinal fluid circulation. In: Bradley, W.G .; Daroff, R.B .; Fenichel, G.M .; Jankovic, J. (eds). Bradley: Neurology in Clinical Practice. 5th ed. Philadelphia, Pa: Butterworth-Heinemann Elsevier; 63
  • Zweckberger, K .; Sakowitz, O.W .; Unterberg, A.W. et al. (2009). Intracranial pressure-volume relationship. Physiology and pathophysiology Anaesthesist. 58: 392-7.

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