Hello. I’m Heather Withrow Today, I will draw what I’ve learned so far about the different eye parts and a little bit about their functions. Let’s start! (Writes “sclera”) (Writes “cornea”) The sclera is the white of your eye The cornea is part of the sclera but it is clear The cornea is responsible for most of your refraction… …meaning it’ll help you see clearly. The sclera helps hold the shape of your eyes …our eyes… yours, mine, which? All of ours. The eye is approximately one inch thick. (Writes “conjunctiva”) The conjunctiva covers… it’s a thin membrane. The cornea… meets the sclera, the white of your eye, that’s where the conjunctiva starts. Inside your eyelids, too. (Writes “choroid”) The choroid has blood vessels that feeds nutrients to the retina. (Writes “retina”) The retina is full of photoreceptors that receives information and sends nerve electrical impulses to the brain through the optic nerve. There are two kinds of photoreceptors: Rods and cones. Rods are responsible for light and detecting movement in dim situations. The second one, cones, their function are for perceiving colors and details. (Writes “optic nerve”) The optic nerve is made up of the same fibers as the retina but there are no cones or rods. That’s why there is a blind spot here. (Points to where the optic nerve leaves the eye.) (Writes “optic disk”, “blind spot”) (Writes “ora serrata”) The ora serrata is where the retina ends but the choroid continues forward, visible… The choroid connects to the ciliary body. (Writes “ciliary body”) Ciliary body… is responsible for the production of aqueous humour, which is… the fluid in the front of the eye. The ciliary body is also responsible for the adjustment of the lens to help with focusing (Writes “iris”) The iris controls how much light enters the eye If it is too bright, the iris will adjust and the pupil will become smaller. If it is dark, the iris will adjust, making the pupil larger. The choroid is connected all the way to the iris. For example, they are the red color here. (points from back to front) (Writes “pupil) The pupil is the opening in the center of the iris. The empty space with the iris ground all around it. (Points to the “fingers” behind the iris.) That’s called the ciliary muscles. Their contribution is helping with the adjusting of the lens. (Draws a vertical, oval lens) (Writes “suspensory ligaments”) (Writes “lens”) The lens is responsible for focusing light rays onto the retina. Remember, I mentioned the cornea starts sharpening up the image 65 percent of the refraction job of the eye The rest of the work, to perfect the image, belongs to the lens. The lens is flattened to see far away, and for seeing closer, the lens thickens. So the muscles, the ligaments and the lens work together as a system. The action (of focusing) is called “accommodation”. (Writes “aqueous humor”) Aqueous humor is a liquid that provides nutrients to the cornea and cleans in side the front of the eye. The ciliary body is behind the iris and is holding the lens in place with ligaments. The ciliary body makes the aqueous which then flows through the pupil and circulates. (Writes “trabecular meshwork”) (Writes “Canal of Schlemm”) With this “iris” the trabecular meshwork is along the outer edge of the iris The aqueous is filtered as it flows through to the Canal of Schlemm, which takes it away from the eye. (Writes “vitreous humor”) The vitreous humor is another liquid and is in the back part of the eye. It helps support the shape of the eye. It is clear. When we are born, the vitreous is gel-like and as we get older it becomes a more fluid liquid. Watery. (Writes “macula”) (Writes “fovea centrals”) The dimple in your retina is called the macula. Not dracula. No. The fovea centralis is exactly in the center of the macula and is responsible for 20/20 to 20/40 vision the macula is responsible for 20/40 to 20/60 vision The macula is strong in cone photoreceptors responsible for details and color. The rest of the retina, along the sides, are full of rods (photoreceptors) which is for light and movement detection in dark situations. An interesting thing that while talking about the eye it reminded me of the Pantheon in Rome It’s a huge, massive dome that is 142 feet wide At the top center of the dome is an opening called an oculus. Which means “eye” The inside of the Pantheon can look like the eye itself I’ll show you now. (Cross-cut illustration of the Pantheon.) The oculus lets light in, brightening the place so you can see inside. Light comes through (the iris) to the retina. Thanks for watching!