Piamadre (brain): structure and functions of this layer of the meninges

Piamadre (brain): structure and functions of this layer of the meninges

When we talk about the human nervous system, which includes the brain, we often forget that this set of anatomical structures could not function well without many other parts of the body associated with it. In particular, both our brain and spinal cord depend on the protection of a series of protective layers known as the meninges.

In this article we’ll see what one of these layers of the meninges, the so-called pia mater , looks like and what functions it performs in our bodies. But first, we’ll briefly go over exactly what the meninges are.

The meninges: definition

The meninges are a series of tissues that cover the central nervous system, offering both protection and support for the circulatory system to deliver blood to many of the areas occupied by neurons and glial cells.

In addition, as we shall see, the meninges also serve to produce cerebrospinal fluid , which fills several spaces in the central nervous system and also fulfils a protective and supportive function for this part of the body (for example, leaving a space between the brain and hard parts with which it can collide).

On the other hand, the meninges are not a homogeneous structure, but are divided into several layers, each with its own properties and different consistency. They are formed by three membranes, placed one on top of the other. They are, from top to bottom, the dura mater, the arachnoid and the pia mater .

What is the pia mater?

As we have seen, the pia mater is the deepest layer of the meninges, which means that it is the furthest from the bones of the skull and scalp.

On the other hand, the pia mater is very thin and has the consistency of a flexible mesh , which makes, for example, that on its surface the furrows and the sutures of the cerebral cortex that it covers are insinuated.

This is because it creates a suitable environment for the ducts that will carry the blood to the brain and spinal cord cells to pass through. Also, because it is so thin, it can adhere well to the contour of the brain.

Types

It is possible to differentiate between two types of pia mater: the cranial and the spinal .

Spinal cord

The spinal pia mater is responsible for wrapping the entire spinal cord from top to bottom.

Cranial pia mater

Although its composition is almost identical to the previous one, its functions are better adapted to the morphological characteristics of the brain.

Functions

Among the main functions of the pia mater are the following.

1. Nervous system irrigation

The pia mater is responsible for providing physical support for the veins, and arteries and capillaries that pass from the external environment to irrigate the tissues of the central nervous system. Thus, their presence enables the neurons and glial cells to survive thanks to the combination of oxygen and nutrients that reach them through the blood .

2. Generation of cerebrospinal fluid

From the pia mater emerge the choroidal tissues , which in turn germinate the choroidal plexuses, places where the cerebrospinal fluid is secreted.

3. A spinal cord cast

The consistency and shape of the spinal cord makes this anatomical structure prone to deformation . However, the pia mater helps to prevent this from happening, as it ensures that everything stays in place and, at the same time, because of its function as a mould, it also prevents it from becoming elongated due to gravity.

4. Create a filter

In a similar way to the blood-brain barrier, the pia mater also serves to try to prevent certain unwanted particles and substances from coming into contact with the neurons and glial cells of the central nervous system. But this protection is more quantitative than qualitative , as the pia mater does not perfectly block the passage of specific elements, but rather limits their diffusion.

5. It leaves a space between the circulatory system and the nervous system

The pia mater is permeable, but at the same time it is dense enough to create a separation between the nervous system and the blood vessels. This causes certain proteins and particles to cross between the two media, ascending or descending from or to the subarachnoid space.

6. Sensory function associated with pain

The central nervous system does not have pain sensors (nociceptors), but the pia mater is in contact with them. That makes certain accidents like herniated discs generate pain , allowing us to know that there is something in our organism that is malfunctioning.

Associated disorders

The main diseases that affect the pia mater are those that end up resulting in an inflammation, which in this case is called meningitis . This health problem associated with the pia mater and arachnoid can be caused by certain bacteria, viruses and fungi, sometimes after having suffered an injury in the area.

On the other hand, the arachnoid, the pia mater and the dura mater can be the place where a blockage of the blood vessels occurs, causing ischemic accidents and aneurysms of different severity.

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