In this video I want to discuss some of the structures of the eyeball.
I'm not going to talk about the muscles that move the eyeball, the extrinsic muscles of
the eye.
We have done a separate video on the muscles of the eyeball already.
So on this view I just want to take care of some of the layers of the eyeball.
The eyeball is actually divided into three layers, also known as tunics.
And from this view we can see the outer white portion of the eye, this is called the fibrous
tunic.
The fibrous tunic is actually divided into two different regions.
The clear part of the eye known as the cornea, and then the white part of the eye known as
the sclera.
So the cornea and the sclera, both part of the fibrous tunic.
Now here we have cut away a portion of the fibrous tunic so that we can look deep to
that.
The next layer in is called the vascular tunic.
And you can see here on this model depicted are blood vessels spread out on the vascular
tunic.
So its name is very appropriate.
From this view of the model we cannot see more of the vascular tunic but when we look
inside the model we will see more of that later.
The last thing I want to point out on this lateral view of this eyeball is the optic
nerve.
The optic nerve, cranial nerve number two, is sensory for vision from the eyeball.
It is slightly to the medial and inferior aspect of the eyeball.
I have removed half of this eyeball so that we can see the other structures.
Again the three tunics of the eye, here we can see the white is the fibrous tunic, then
we see a brown layer, which is our vascular tunic, and then we see a pinkish layer.
That is the nervous tunic.
Some books call it the retinal tunic.
And it makes up the retina.
If we come toward the front of the eyeball again we see the sclera and the cornea.
Both part of the fibrous tunic.
The vascular tunic posteriorly is known as the choroid.
And then as we come forward it widens out into an area known as the ciliary body.
And the ciliary body will have ciliary muscles which will control the shape of the eye lens.
We will talk about that briefly.
And it also extends forward so that the vascular tunic makes up the colored part of our eye
known as the iris.
So the iris is part of the vascular tunic of the eye.
And then in the middle we have the structure known as the pupil.
The pupil is actually the anatomical lack of a structure.
It is an opening in the middle of the iris.
Directly posterior to the pupil we see the lens of the eye.
From this angle that actually defines some different chambers of the eye.
We have the anterior chamber of the eye, which is located between the cornea and the iris.
That is known as the anterior chamber of the eye.
It is filled with a fluid known as aqueous humor.
Between the pupil and the lens, or between the iris and the lens, very hard to see on
this model, is a much smaller chamber known as the posterior chamber.
That chamber is also filled with aqueous humor.
It is in continuity with the anterior chamber through the opening of the pupil.
Behind the lens of the eye we have what is known as the vitreous chamber.
The vitreous chamber is not filled with aqueous humor.
It is not filled with vitreous humor.
It is filled with a jellylike substance known as the vitreous body.
Vitreous body.
Now notice on the posterior portion of this eyeball, right here, we have a white spot.
That corresponds to where the optic nerve entered the eye.
There are no photo receptors of the retina at that spot right there, so it is often referred
to as the blind spot.
Its anatomical name is the optic disc.
Also known as the blind spot because any light focused on that portion of the retina will
not stimulate any sense of vision.
Now I rotate this model just slightly, we can see as the retina comes forward and meets
the portion of the vascular tunic coming back from the ciliary body, we have a serrated
edge.
That serrated edge is known as the ora serrata.
The ora serrata.
I want to take just a little bit of time to focus in right here on the ciliary body.
In that ciliary body I said they were ciliary muscles.
And those ciliary muscles attached to small ligaments known as the suspensory ligaments
of the lens.
Those fibers will attach into the lens so that by putting tension, or releasing tension
in those ciliary muscles we can control the shape of the eye lens.
I will leave it to your individual lecture profession as to what they want you to know
about that particular structure.
From this angle of the eyeball we can see some other things that weren’t shown on
the other side of the model.
A quick recap though, the white is our fibrous tunic.
The brown, our vascular tunic.
Here as the choroid and here as the ciliary body and here as the iris.
We can see anterior chamber.
The posterior chamber we have to imagine because we do not have the lens.
And then the vitreous chamber.
But I want to focus on the back of this vitreous chamber.
Here we see somewhat of a brownish spot or sort of a peach color.
That is called the macula lutea.
The macula lutea.
And in the very middle of that macula lutea we see a yellow spot known as the fovea centralis.
The macula lutea is very good color vision.
There are more cones in that area than there are rods.
And in the very middle of that macula lutea when we get to the fovea centralis we have
our very best focused vision, and it is mostly color vision.
That area, that yellow spot, known as the fovea centralis.