 We're going to cover most of the anatomy of the eye, we've already talked about the chambers and accessory structures. We're going to focus on the eye. Here you see orbital fat which just fills in the orbit and helps cushion and insulate the eye. We're going to focus on the three layers or tunics of the eye. We have the outer fibrous tunic, the middle vascular tunic, and the inner neural tunic. So we'll hit all the key structures one layer at a time. Let's go ahead and start with this outer fibrous tunic. This is going to be really only two things are going to be here and you're going to have your sclera and your cornea. So the outer fibrous portion of the eye is broken down into those two parts. The cornea is the transparent portion at the front of the eye which has to be transparent or else things couldn't reach the retina of the eye and you couldn't see them. So the cornea is going to be the transparent portion of the eye, the sclera is going to be the white of your eyes. So those are the two parts of the outer fibrous tunic, cornea and sclera. The middle vascular tunic, also known as the uvia, is going to have three different sets of structures here. The iris, the ciliary body and the coroid. So take those in order. So the iris is going to have muscle fibers that change the diameter of your pupil depending on how much light there is. If you have lots of lights shining on me, so right now my pupils are pretty constricted. If I were to turn all the lights off, my pupils would dilate to try to get every full ton of light into my eye as possible. So we have the papillary constrictor muscles are the ones that constrict the pupil and close down the diameter of the eye. The papillary dilator muscles would do the opposite. So that's the job of the iris to control the diameter of the pupil. Next we have the ciliary body which is made of the ciliary muscle and the ciliary processes which attach directly to what are called the suspensory ligaments of the lens. So the ciliary muscle is this circular muscle that's attached to the entire lens on the outside and by contracting and relaxing can tug on the lens or relax, changing the shape of the lens which changes where light or where images are focused on the retina. So your lens is full of these cool transparent proteins called crystallines and just like ground up glass is used to make other types of lenses, your lens uses these crystalline proteins to refract light to focus images in this case on the photoreceptors of the retina, the rods and cones. So the ciliary muscle is what controls the shape of the lens which controls what we're focusing. A flat lens is good for seeing things far away, for far vision, a more rounded lens is good for near vision. We'll cover vision and visual acuity in a separate video. All right, so that's going to be the ciliary body and then how it controls the lens there is a very important structure. The last part of this middle tunic here is the coroids. You see the coroid there, it supplies the outer retina with nutrients then helps maintain the temperature and volume of the eye, so that's important. Now we're at the actual functional part of the eye, everything about the eye is designed to get what we're looking at, the images we're seeing, the light that's entering the eye to strike the photoreceptors of the retina. So the neural tunic is your retina and it's got support cells of course, but it has an outer pigmented part and interneural part, but the key here is the actual visual receptors and that's going to be the photoreceptors, the rods and cones. So really big picture and I'll do a separate video on rods and cones. They do not discriminate amongst colors. They see the world in gray scale, but they're highly sensitive to light. So rods are really good for peripheral vision because they're out on the edges of the retina and they're really good in low light situations. They can track like moving targets, but the images are fuzzy, there's no color discrimination, but they're very, very important from a survival standpoint, especially in low light. The cones, they see colors, they see fine edges, they see clearly, they see in color. So this is going to be really, but they're only going to be found in the center of the retina. So for central vision. So for rods, think peripheral vision, low light, do not discriminate color. Cones clear vision right in the center of your visual fields, but they do discriminate color. So I'll go a little more detail about wavelengths and stuff like that in a separate video. So as far as the cones go, so cones are clearly, if you want to see something, you make sure the lights are on and you look right at it, right? And that's because the cones are going to be densely clustered in this area called the phobia or the phobia centralis, which is actually in a larger area called the macula lutea. So if you're looking right at something, it's the, those photons are going to strike the macula lutea and the right in the middle of that, you'll have the phobia centralis. So this is going to be, there's only cones here. So you're going to see nice discriminating, you know, color discriminating clear images when you look at something directly. So I think it goes without saying, make sure the lights are on and you're looking right at something if you want to see it. All right. Cause that's because that's where visual acuity is going to be the greatest. Now we could go into a little more detail and just say that, you know, each of these photoreceptors has its own retinoganglion cells sending information to the brain. So if you're looking right at something, your brain knows exactly what you're looking at and exactly where you're seeing it. Whereas peripheral vision, you might have 50 of these photoreceptors, these rods attached to a single retinoganglion cell. So you don't, everything's blurry. There's no, there's no fine edges, these types of things. All right. Last thing to note here about this inner neural tunic or your retina is where the optic nerve actually exits the eyeball. There's going to be an area where there aren't any photoreceptors. That's called the optic disc and that's, that's what creates our blind spot. So each individual eye does have a blind spot. There's a part of the retina that doesn't actually send visual signals to the brain. Thankfully we have binocular vision. We have two eyes. So we don't really have a blind spot, but you can do activities where you can find the blind spot in one eye. It's pretty cool. So the optic disc creates the blind spot. All right, those are all of the key structures of the eye that you need to know. I hope this helps. Have a wonderful day. Be blessed.