Welcome. In this lecture, we will talk about the brain and the cranial nerves.
So first, let us look at the principal parts of the brain.
The outermost part of the brain is known as the cerebrum.
This is what you would see if you are holding the brain in your hand.
The innermost part of the brain are the ventricles.
The ventricles are empty cavities inside of the brain that actually hold the cerebrospinal fluid.
The next part of the brain is the diencephalon.
The diencephalon is made up of 3 major parts.
You have the hypothalamus, the epithalamus, and the thalamus.
The next principal part of the brain is going to be the brainstem.
The brainstem sits just inferior to the cerebrum.
It includes the midbrain, the pons, and the medulla oblongata.
The next part of the brain is the cerebellum.
The cerebellum sits inferior to the cerebrum and posterior to the brainstem.
The cerebellum as 2 major parts.
You have the outer cerebellum cortex which is gray matter and on the inside,
you have the white matter which we refer to as the arbor vitae because of its tree shape.
The brain is protected by 3 major layers.
The outermost layer of protection is going to be the cranial bones or your skull.
The next layer protection is going to be a connected tissue layer known as the cranial meninges.
This is going to include the pia mater, the arachnoid mater, and the dura mater.
The last layer of protection of the brain is going to be the cerebrospinal fluid.
So if we take a closer look at the meninges of the brain,
we will notice that we had the arachnoid mater which is very similar and continuous
with the arachnoid mater of the spinal chord and just deep to the arachnoid mater,
we have what's known as the subarachnoid space.
This space is important because this is where the cerebrospinal fluid is going to be located.
Deep to the subarachnoid space and to the arachnoid mater
and continuous with the lining of the actual cerebrum, we have the pia mater.
The outermost layer of our cranial meninges is actually the dura mater.
Unlike the spinal chord which only has one layer, the dura mater has 2 layers.
These 2 layers are mostly fused together except where they separate
in order to enclose the venous sinuses of the dural part of the brain.
These sinuses are there to drain venous blood from the brain
and deliver that venous blood to the internal jugular vein which then will eventually return to the heart.
These are normally known as the superior sagittal sinus
and there's also other sinuses throughout the brain as well.
The space between the dura mater and the arachnoid mater
is known as the subdural space and in this space we have interstitial fluid.
Another structure that's important and a part of the cranial meninges
is known as the arachnoid granulation villi.
These structures are important for re-absorption of cerebrospinal fluid.
Don't worry, we'll talk a little bit more about that shortly in the lecture.
So the dura mater also has different extensions.
The dura mater extends down in order to separate the 2 hemispheres
and this extension is known as the falx cerebri.
The next extension is the falx cerebelli.
In this extension, we are going to separate the 2 hemispheres of the cerebellum.
The third extension of the dura mater is the tentorium cerebelli.
This extension separates the cerebrum from the cerebellum.