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The human eye is a sense organ that reacts to light and allows vision. Rod and cone cells in the retina are photoreceptive cells which are able to detect visible light and convey this information to the brain. Eyes signal information which is used by the brain to elicit the perception of color, shape, depth, movement, and other features. The eye is part of the sensory nervous system. Here are 12 basic parst od the eye:
- 1. Cornea - The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber.
- 2. Sclera - The sclera, also known as the white of the eye is the opaque, fibrous, protective, outer layer of the human eye containing mainly collagen and some crucial elastic fiber.
- 3. Choroid / Choroidea - Choroidea is the vascular layer of the eye, containing connective tissues, and lying between the retina and the sclera.
- 4. Retina - The retina is the innermost, light-sensitive layer of tissue of the eye. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which translates that image into electrical neural impulses to the brain to create visual perception.
- 5. Fovea centralis - The fovea centralis is a small, central pit composed of closely packed cones in the eye. It is located in the center of the macula lutea of the retina. The fovea is responsible for sharp central vision, which is necessary in for activities for which visual detail is of primary importance, such as reading and driving.
- 6. Ciliary body - The ciliary body is a part of the eye that includes the ciliary muscle, which controls the shape of the lens, and the ciliary epithelium, which produces the aqueous humor.
- 7. Aqueous humour / Aqueous body - The aqueous humour is a transparent water-like fluid similar to plasma. It is secreted from the ciliary body, a structure supporting the lens of the eyeball.
- 8. Iris - In humans and most mammals and birds, the iris is a thin, annular structure in the eye, responsible for controlling the diameter and size of the pupil, thus the amount of light reaching the retina. Eye color is defined by that of the iris.
- 9. Pupil - The pupil is a black hole located in the center of the iris of the eye that allows light to strike the retina. It appears black because light rays entering the pupil are either absorbed by the tissues inside the eye directly, or absorbed after diffuse reflections within the eye that mostly miss exiting the narrow pupil.
- 10. Lens - The lens is a transparent biconvex structure in the eye that, along with the cornea, helps to refract light to be focused on the retina. By changing shape, it functions to change the focal length of the eye so that it can focus on objects at various distances, thus allowing a sharp real image of the object of interest to be formed on the retina.
- 11. Vitreous humor - The vitreous body is the clear gel that fills the space between the lens and the retina of the eyeball of humans and other vertebrates.
- 12. Optic Nerve - The optic nerve is a paired cranial nerve that transmits visual information from the retina to the brain.
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