The structure of the human eyes is one of the most important and complex in the human body. Eyes are used to see and process visual sensory information, but eyes can only see if there is light. When it is dark and no light enters the eyes, the eyes cannot see because they are optic structures that require light to function. There are two types of structures that make up the eye: internal and external. In this article, we’ll discuss both types of structures which together make up the human eye.
Structure of the human eye
The first external portion of the eye is called the cornea. The cornea is the strong, translucent outer surface of the eye, which receives light and allows it to continue into other structures of the eye. Its most important function, however, is to protect the softer, more sensitive eye structures beneath the cornea.
Another exterior structure of the eye is the iris, which is the part of your eye that is colored. For example, the iris may be blue, green, brown, hazel or gray. The iris is a diaphragm which opens and closes to adjust the size of the pupil to regulate how much light can enter the eyes. The opening in the iris the known as the pupil, and it is through this hole that light is able to travel from the exterior to the interior of the eye.
Below the cornea is the aqueous humor, which is a jelly-like substance located in the anterior cleft of the eyes. Its function is to refract light as it enters the eyes and travels to the lens. The lens has the important role of positioning the shadow along the optic nerve. Special muscles cause the lens to change shape in order to focus on objects close up or far off in the distance. A substance called vitreous humor allows light to travel from the lens to the retina, which is a light sensitive structure behind the wall of the eyes. It is responsible for catching the light and sending the visual signal to the brain via the optic nerve.