The Function of the Cranial Meninges
Today we will look at the layer of supportive and protective tissue that separates the skull and the brain.
The main functions of the meninges include:
- Protecting the brain and spinal cord from mechanical injury
- Providing blood supply to the skull and to the hemispheres
- Providing a space for the flow of cerebrospinal fluid.
3 Main Layers of the Cranial Meninges
The Dura Mater
The two layers of the Dura mater are,
- The endosteal layer: This is the thickest layer and it lines the skull.
- The meningeal layer: This layer lines the endosteal layer most of the time, except in a few places such as the falx cerebri and the tentorium cerebelli. At these places, the meningeal layer actually separates from the endosteal layer and “sinks down” between the left and right hemisphere for the falx cerebri, and between the occipital cortex and the cerebellum for the tentorium cerebelli.
Here is a hint for remembering what tentorium cerebelli stands for: The word “tentorium” comes from the word “tent.” You can visualize those old tents that had the curved shape of Chinese temple roofs. If you look at the brain and the cerebellum from the back, you will see that the space in between them kind of looks like that shape… Thus, the name “tent of the cerebellum”, or “tentorium cerebelli” in Latin.
As it “sinks down” the meningeal layer creates a space between the endosteal layer. This space can house the sinuses.
2 Interesting Facts About The Dura Mater:
- The dura mater has its own blood supply that comes from a set of meningeal arteries, the main one being the middle meningeal artery.
- The dura mater is pain-sensitive. Yes, the rest of the brain is not sensitive whatsoever, but the dura mater is innervated by trigeminal nerves (mostly).
The Arachnoid Mater
The arachnoid layer is located right under the dura mater.
If “arachnoid” makes you think of spiders, you are in the right direction. The arachnoid layer is actually filled with an intricate “web” of collagen.
I like to think of this layer as a sort of mattress filled with collagen instead of springs, that dampens any shock the layer may receive.
The pia mater is the innermost layer. Right in between the arachnoid layer and the pia mater is a space called the subarachnoid space. This subarachnoid space houses the brain’s cisterns (“pools” of Cerebrospinal Fluid) as well as cerebral arteries and veins.
The Pia Mater
The pia mater is the innermost layer lining the brain.
In fact, it completely lines every sulci and gyrus of the hemispheres, contours the brainstem, and all the folds of the cerebellum. It is very tender (pia means tender in Latin). It can be very easily damaged while performing dissections.
The pia mater also plays a role in the formation of the choroid plexus (for the lateral, 3rd, and 4th ventricles).
Together, the arachnoid layer and the pia mater are called the leptomeninges.
Minimum to remember:
- There are 3 layers of protection and support between the brain and the skull: The Dura mater, the arachnoid layer, and the pia mater.
- The dura mater is the “toughest” layer, and the pia mater is the “softest” layer.
- The arachnoid layer is filled with a web of collagen.
- All together these three layers are called the meninges.
- The arachnoid layer and pia mater layer are together called the leptomeninges.
If you want more articles and videos about the Nervous System, you can find them here. More resources are available to help make Biology fun. I invite you to absorb all the content you can find here at Interactive-Biology.com.