How brain covers protect the brain: Journeys to the brain -1

This journey begins with a visit to the brain covers. Starting from the hard bony skull, another three layers, called meninges, inside the skull provide different kinds of protection to the brain. At the same time, they carry out various tasks.

Join this journey!

Our brain is a very pliable organ. Even a finger pressure can make a dent over its surface. Therefore, it needs good protection. Fortunately, very hard skull bones provide that protection. Inside the skull, three layers cover the brain. They prevent friction as well as act as a cushion. However, that is not their only job.

The outermost brain cover: Dura mater (“tough mother”)

The outermost cover is the thickest and the firmest of all three; hence the name: Dura mater meaning “tough mother”.

Now, look at Figure 1; It is an old drawing that shows only the left half of the Dura mater. In reality, it glistens and transparent. Because of its transparency, we can see a lot of trees like branches that run throughout inside the cover. In fact, these are blood vessels. The Dura mater is directly attached to the inside skull bones.

view Brain: dissection showing the top of the brain, with the dura mater of the left hemisphere and the gyri of the right. Watercolour after(?) W.H. Lizars, ca. 1826.
Figure 1: Dura mater
Credit: Brain: dissection showing the top of the brain, with the dura mater of the left hemisphere and the gyri of the right. Watercolour after(?) W.H. Lizars, ca. 1826. Credit: Wellcome CollectionAttribution 4.0 International (CC BY 4.0)

Other two brain covers: Arachnoid mater and Pia mater

Now, we look at the two inner covers. Inside the Dura matter, the other two thinner coverings (Figures 2 and 3) spread all over the brain surface. These covers are also transparent. Unlike the outer covering, they wrap the brain surface tightly throughout all grooves and bumps of the brain surface. The middle layer is full of fluid, called cerebrospinal fluid.

This image shows a cross-section through the brain. The different meningeal layers are labeled.
Figure 2: Dura mater and Pia mater;
source: openstax.org, RICE University
under the CC BY 4.0 license
figure1
Figure 3: Brain covers and blood carrying vessels;
Source: BioMed Central, a part of Springer Nature Natividad et al. under the CC BY 4.0 license.

In-between the two layers harbor a fluid – named cerebrospinal fluid (in short CSF). Not only that, small branches of arteries traverse throughout the layers. They carry oxygen and food to the neuron forest and other structures.

Why should we know about this?

Why should we know this information? This is the reason; when a small branch of artery bursts or damages blood leaks out and fills the space between the two covers. Depending on the volume, the leaked blood builds pressure on the pliable brain surface. As a result, it may exert pressure over neurons in that area. This undue pressure disrupts its job. Sometimes this pressure may even cause death. It has to be stopped.

An excellent video clip can be found from the University of Utah through this link: https://neurologicexam.med.utah.edu/adult/html/brain-dissections.html#10

Author: Prasantha De Silva

Leave a Reply

Your email address will not be published.