The exterior functions and structure of a human eye are the human eye has eyelids, eyelashes, eyebrows to protect the eye from any unknown substances. The human sclera is white, the color changes the way the eye sees things. The human eye color changes depending on the amount melanin that the eye contains, the less the lighter, the more the darker. The human pupil gets smaller when no light is hitting it, and gets bigger when light is hitting it. The human eye has reflexes that react in a different way than a eagles, for example when an unwanted object touches the eye, the human eye is forced to cry to get rid of the object, this is to protect the eye from getting damaged.  

      Let's talk about the human eye it's self. There are 5 major parts of the human eye: Cornea, which is a clear, thin, and curved object that covers the eye. The cornea is also the first layer of the eye, it protects it from anything that might enter the eye or damage it.

     Next, we have the lens, a clear, curved object that has a different index of refraction than its surrounding medium. It focuses rays of light as to form an image on the retina. The lens has three parts, which are the capsule, the cortex, and the nucleas. It is located directly behind the iris and the pupil. 

     Next is the iris. The iris controls the size of the pupil depending on how much light the eye is recieving. The iris is also the colored object that surrounds the pupil. So some people's iris is brown, others is blue, green, hazel, all of these colors are the surrounding of the pupil, also known as the iris. 

     The retina, the third layer of the eye. The retina is where the images end up, sent by the lens and the cornea. The retina is located at the back of the eye, where the image is recieved and sent to the optic nerve of the brain. 

     The last main part of the eye is the optic nerve, which is sometimes called the cranial nerve II, which in words is when the retina recieves the image, it then sends information to the brain.