Meninges: anatomy, parts and functions of the brain

The meninges are one of the most important parts that cover the central nervous system. They surround both the brain and the spinal cord, and perform several very important functions in keeping these body structures in good condition.

In this article, we will see what the meninges are, what are their parts and what functions they perform.

    What are the meninges?

    The first thing that comes to your mind when you see meninges without special measuring instruments is that they form a kind of membrane that surrounds the brain, Acting as a kind of outer layer that sits just below the bones of the skull. For this reason, it is most common to think that they are, above all, a protective element, which provides beating and reduces the chances that the elements introduced into the skull (breaking the bone) cause damage to the brain.

    It makes sense to be like that. Regardless of the high levels of sedentary lifestyle observed in the population, as a rule, we humans are constantly on the move.

    We walk, run, dance, jump, interact with the environment and other individuals … all these actions can cause that in certain circumstances the organs that are part of our body, including those of the nervous system, they run the risk of being damaged.

    This is why the presence of protective systems is necessary to keep everything in place and to block the arrival of possible injuries. Fortunately, our body benefits from different structures that allow us to protect our viscera, organs and internal structures. In the case of the nervous system and the brain, it is protected by the skull and spine, as well as other structures and elements such as the blood-brain barrier or, in our case, a series of membranes called meninges.

    The functions of this part of the human anatomy

    Imagine that we are at an operating table and we have to walk to a part of the patient’s brain. After passing through a layer of skin and muscle, we reach the skull, a bony structure that protects the brain. However, if we go through this bone protection we are not directly in contact with the brainBut we would find a series of membranes surrounding the nervous system. These membranes are called meninges and are very important for our survival, to the point that infection in them can put us in danger of death.

    The meninges are a collection of protective layers located between the central nervous system and its bony protection, Both in the brain and in the spinal cord. More precisely, there is a series of three membranes located one below the other, receiving from the most external to the most internal the name of duramater, arachnoids and piamater. Thanks to them, circulate different fluids that help to keep the brain clean and nourished, being crossed and irrigated by different blood vessels,

    While when we talk about the meninges we mainly think of the membranes that cover the brain, it is important to note that these structures they cover the whole central nervous system and not just the brain, Also protects the spinal cord.

    The three meninges

    As indicated above, by meninges is meant a set of three membranes which internally protect the nervous system.

    From the most external to the most internal, they are as follows.

    1. Duramadre

    In addition to being the outermost meninges, duramater is the hardest and most condensed of the three of those we have, and it is also the one that is closest to the outside. Attached in part to the skull, this membrane protects the brain and provides structural support to the entire nervous system by dividing the cranial cavity into different cells.

    In the dura are most of the large blood vessels of the brain, Because in addition to protecting them, it allows them to have a space through which to distribute themselves and move from one place to another. Subsequently, these blood vessels will diversify into different subdivisions as they deepen in the brain.

    • To learn more about this layer of the meninges, you can consult this article: “Duramadre (brain): anatomy and functions”

    2. Arachnoids

    Located in an intermediate zone between duramater and piamater, the arachnoid is a meninge that receives its name due to its morphological resemblance to a spider’s webIn other words, your grid setup. It is the most delicate of the three meninges, a transparent, non-vascularized layer attached to the dura.

    It is mainly through these meninges and the space between the arachnoid and the pyramid that the cerebrospinal fluid circulates. In addition, it is in the arachnoid where the end of the life cycle of the cerebrospinal fluid takes place, which is returned to the blood flow through the villi or structures known as arachnoid granulations in contact with the large veins that they cross the dura.

    3. Our mother

    The meninges are more internal, flexible and in greater contact with the structures of the nervous system is the piamadre. Many blood vessels can be found in this layer which supply the structures of the nervous system.

    It’s a thin membrane that stays attached and seeps through cracks and convolutions of the brain. In the part of the piamater in contact with the cerebral ventricles, we can find the choroid plexuses, structures in which the cerebrospinal fluid that supplies the nervous system is synthesized and released.

    Spaces between the meninges

    While the meninges are located one behind the other, the truth is that some can be part of it. intermediate spaces through which cerebrospinal fluid flows. There are two intermediate spaces, one between the duramater and the arachnoids called the subdural space and another between the arachnoid and the piamater, the subarachnoid. It should also be mentioned that in the spinal cord we can find one more space, the epidural space. These spaces are as follows.

    1. Subdural space

    Located between the dura mater and the arachnoids, the subdural space is a very slight separation between these meninges through which an interstitial fluid circulates which bathes and nourishes the cells of the different structures.

    2. Subarachnoid space

    Under the arachnoid itself and in contact with the arachnoid and the piamater, we can find the subarachnoid space, through which cerebrospinal fluid flows. In some areas of the subarachnoid space, the separation between the arachnoid and the piamater widens, forming large cerebral cisterns from which cerebrospinal fluid is distributed to the rest of the brain.

    3. Epidural space

    While in the brain the outermost layer of the dura mater is attached to the skull, in the spine the same thing does not happen: in the spinal cord there is a small separation between the bone and the spinal cord. This separation is called the epidural space, be in its connective tissue and lipids that protect the bone marrow when we move or change position.

    This is where the epidural anesthesia is injected in women in labor, blocking the transmission of nerve impulses between the spinal cord and the lower body.

    Functions of the meninges

    The existence of meninges is a great advantage for humans when it comes to maintaining the functioning of the nervous system. This is because the membranes they perform a number of functions that allow adaptation, Which can be summarized as follows.

    1. They protect the nervous system from physical injury and other damage

    The meningeal system as a whole is a barrier and shock absorber that prevents or prevents blows, traumas or injuries causing serious or irreparable damage to the body. central nervous system, whether it is the skull or the spinal cord. We must keep in mind that these structures are essential to our survival and at the same time relatively delicate, so they need several layers of protection that separate them from the outside environment.

    They also act as a filter which prevents harmful chemicals from entering the nervous system. In other words, the meninges offer protection consisting of a physical and at the same time chemical barrier. However, this barrier can be crossed by certain substances, vulnerabilities therefore remain to be considered.

    2. It keeps the brain environment healthy and stable

    It should be noted that the brain is a delicate body, very vulnerable to blows or injuries, and that it can even be deformed with some ease. In addition, it must be constantly fed.

    The meninges are involved in the genesis and allow the circulation of cerebrospinal fluid, a key element in the elimination of waste generated by continuous brain function and maintain intracranial pressure.

    Other fluids, such as the interstitial, also flow through this system, allowing the aqueous medium in which the nervous system is located to be stable. In addition, the blood vessels that supply the brain pass through the meninges, I also feel protected by them. In conclusion, the meninges they work by facilitating the survival and nutrition of the nervous system.

    3. Keep the nervous system in place

    The presence of the meninges prevents the nervous system from moving too much, fixing the structures that are part of it to a more or less stable situation and causing the maintenance of a fixed internal structure, As in the intracranial cavity and its division into cells. This is important because the consistency of most parts of the nervous system is almost gelatinous and therefore should not be held in place. To do this, you need a coating that is in contact with all your corners, and that does not let it “dance” inside our body.

    In short, the meninges act like a band and give shape and unity to this whole part of the nervous system, which allows it to function normally.

    4. Inform the body of possible problems

    Although the perception of stimuli and internal states of the body is given by the action of the nervous system, the central nervous system itself does not have receptors on its own that signal internal problems, such as nociceptors. However, a set of organs as important as the brain needs to be very protected, so that at the slightest sign that something is wrong, you can react quickly and move away from danger.

    Therefore, although the brain does not have receptors for pain or any other sensation related to the physical stimuli applied to it, fortunately the meninges do not, which are not. they have receptors for tension, expansion, pressure and pain and therefore report on what is happening in this part of the internal environment.

    Thus, it is thanks to them that it is possible to detect the existence of neurological problems (in addition to the fact that these problems lead to other problems of perception or behavior), headaches being the product of alterations of these membranes.

    Bibliographical references:

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    • Martinez, F .; Tomorrow, G .; Panuncio, A. and Laza, S. (2008). Anatomo-clinical examination of the meninges and intracranial spaces with particular reference to chronic subdural hematoma. Mexican Journal of Neuroscience: 9 (1): 17-60.
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