Structure of the Eyeball - Video Tutorials & Practice Problems

Eyeball

As we learn about our sense of sight, we're gonna spend a lot of time talking about the structure of the eyeball. Now, to me and to a lot of people, the structure of the eye is one of the most amazing products of evolution. We have this structure that's able to focus electromagnetic radiation in a way that we're able to perceive vibrant colors and see three dimensional images that all works kind of blows my mind, but it does work and we largely understand how it works and like so many things comes back to structure. So we're gonna start by saying that the eyeball is this irregularly shaped hollow sphere. You know, it's basically this small ball with some bumps on it and the ball, the outside of that ball is made up of three layers that surround what we're gonna call on the inside the optic components. Now, as we go through this, we are gonna go through all of this information more in a lot more detail. Right now, we just want to step back and see the entire picture so that when we get to that detail, you have a better frame of reference So for structure, we're gonna start with the outside and we're gonna work our way in. So we're gonna start with the fibrous layer, fibrous layer is the outer layer and it's there for structure protection and also for muscle attachments. So if you move your eyeballs back and forth, that's because there's muscles attached to this fibrous layer, pulling on the eye back and forth. Now, you can also touch your eyeball or poke yourself in the eye. I don't recommend it. But if you do, you'll probably be OK because this fibrous layer is on the outside and it's really tough providing protection. Now, as we look at our image here, we see a cross section of the eye and in blue, we see this fibrous layer going all the way around. We can see though that we have two shades of blue. Here in the front, we have that light blue. That's the cornea. The cornea is the front of your eyeball that is clear so that you can see through it. The rest of it we have here in this darker blue, that darker blue represents the sclera, the sclera, sometimes you just call that the white of your eye. All right. So as we move in from the fibrous layer, we reach the vascular layer, vascular layer is the middle layer and sometimes it's called the UVEA. Now, I'm not gonna call it the UVEA going forward, but you should be familiar with that name because sometimes it comes up, the vascular layer is there to control the light and also provide blood supply. So as we look at the eye here, you can see going all the way around inside that fibrous layer, we have that vascular layer and it's gonna be made up of three smaller parts. The iris, the iris is here in front, that's the color of your eye. And it's responsible for controlling how much light actually enters the eyeball. We have the ciliary body which you see here on the sides there. The ciliary body is largely responsible for changing the shape of the lens. It has muscles in it that can pull or relax. And when it does that, it changes the shape of the lens and allows your eye to focus and then going around the back, we have what's called the choroid. And again, this is the vascular layer. So that's where a lot of that blood supply for the eye is the chid. Also though has some pigment in it because when light light comes into the eye, you don't want it bouncing all around any light that isn't absorbed by those photoreceptor cells you want absorbed in the back of the eye. So it doesn't cause artifacts in your vision. That's the job of the coro all right, as we move in from the vascular layer, we reach the inner layer. And the inner layer is often just referred to as the retina. The retina is where you have your photosensitive cells and your nerve cells. So for vision, this is really where the rubber hits the road. These are the cells that are picking up the light and then sending those messages to the brain. So we can see in our image here all around the back, you have those photoreceptor cells. But then to get the image to the brain, you need these nerve cells that are connecting all these photoreceptor cells running through the retina and then they're gonna run out and down the optic nerve so that the image can get to your brain. All right, we just really have one structure here. That's the retina, but the retina is a really complex structure that we're gonna go into a lot of detail on going forward. All right. Finally, inside the eye, we have what we're gonna call the optic components. We're saying this is the inside of the eye and we're gonna say that this transmits and focuses light. So these are the clear components that fill up your eye. And there's really three things here. We have the aqueous humor, the vitreous humor and the lens. All right. So the aqueous and the vitreous humor, the aqueous humor is here in purple. It's a liquid that fills up the front of the eye. The vitreous humor is here in pink. It's a gel like substance that fills up the majority of the eyeball. Again, both of them are clear and really their job is just to fill up that hollow space of the eye and allow light to pass through. Then we have the lens, the lens is this sort of relatively hard but flexible structure there. And it is there to focus the light, the light that enters passes through the lens gets focused on the retina. So we can see a clear image, right? We just went through this sort of from outside to inside as we go through this going forward, we're gonna sort of approach it as light passes through the eye. The one change that we have then is we're gonna talk about the optic components before we talk about the retina, I'm looking forward to it. I'll see you there.

Structure of the Eyeball Example 1

Our example tells us that in the following image, four important structures, the eye are labeled based on their location, identify which layer of the eyeball they are part of then identify how each structure primarily interacts with light. And for interaction with light, we have three options. It says if the structure transmits light, mark it with A T, if the structure controls light, entering the eye mark it with ac if the structure absorbs and responds to light, mark it with an R. All right. So before we look at these very specific structures, let's remember those general layers that we learn, we had the fibrous layer, the vascular layer, the inner layer and then filling up the eye with a clear optical components. All right. So with that in mind, let's see what we got here. So first up, we have the cornea and we have this image of the eye here. And this arrow is pointing to this very front of the eye. So which layer is that that outer very front layer? Well, that was the fibrous slayer, the fibrous layer. Remember that's the entire outside of the eye, the cornea, the clear part in front and the sclera, the white of the eye all around the back. All right. So how does the cornea interact with light? Well, as light hits the eye, it's gotta go through the cornea. So I'm gonna say the primary function of the primary way that the cornea interacts with light is to transmit light. I'm gonna mark it with A T All right. Next up, we have the iris. So we have arrows right here pointing to the iris right here. Do you remember which part of the eye or which layer of the eye is the iris? Part of? No, that would be the vascular layer. The vascular layer sometimes also called the Juvia, right had blood vessels in it, but in the front here, it had that iris which is the color of your eye and its job is to block light coming in the eye. The only way that light can get in the eye is through the pupil, the hole in the middle of the iris. So then giving it that way, how would you say that the iris interacts with light? Well, I would say that it controls the light entering the eye. I'm gonna mark it with ac All right. Next up, we have the lens. All right, the lens is right here. This structure right here in the eye. Do you remember which layer of the eye? The lens was part of now the lens is part of those clear components inside the eye. And we refer to those as the optical components. And now when you think of the lens, how would you say that it interacts with light? Does it transmit control or respond to the light? Well, I'm gonna actually mark it with two things, right? Because the lens is definitely clear. So light goes through it, so it definitely transmits light. So I'm gonna mark it with A T but it's also focusing the light. So when it focuses the light, I'm gonna say it also sort of controls the light, it bends the light so that you can focus it and have a clear image on the red. All right, that brings us to the Foia central, the foa centrals is gonna be the center of the retina. So the retina, what layer did we say the retina was? Now we said the retina was the inner layer. And how does the retina interact with light? Well, of these three options, there's one we haven't chosen. The retina responds, it absorbs and responds to the light sends in it a message to your brain to perceive an image. OK. Now, these are structures that are more detailed than you need to know quite yet. We're gonna learn all of these in a lot more detail coming up right now. You just wanna sort of organize this structure in your head and sort of think in grand schemes. How do these different things work and work with each other. Right. More practice problems to follow. I'll see you there.

Identify the layer or layers of the eye that function to protect the eye.

• A. Fibrous Layer.
• B. Vascular Layer.
• C. Inner Layer.
• D. Both A and C are correct.