The 11 parts of the eye and their functions

Vision stands out among human sensory-perceptual systems due to its high complexity. The structure of the eye, the main organ of sight, is a good example of this, to the point that it has reached be used as a supposedly irrefutable argument by those who defend that life was created and designed by a God.

Analysis of the parts of the eye It can be greatly extended as the organs of vision are made up of many structures. In this article we will focus on the main ones and on the general description of the transduction process that makes light energy come to be perceived as images.

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What is the eye?

The eyes are the foundation of the visual system. These organs transform light energy into electrical impulses that, when transmitted to the visual cortex of the occipital lobe, allow three-dimensional perception of shape, movement, color and depth.

The eyeballs are spherical in shape and have a diameter of approximately 2.5 cm. They are divided into two sections: the anterior and posterior chambers, respectively filled with aqueous and vitreous humor, fluids that regulate intraocular pressure. The anterior chamber is smaller and is located between the cornea and the iris, while the posterior chamber is made up of the other parts of the eye.

Unlike what happens with other sensory organs, the eye is partially derived from the central nervous system. Specifically, the retina, which receives light information, develops from the diencephalon, the embryonic structure that also gives rise to the brain hemispheres, the thalamus and the hypothalamus.

In the retina we find two types of photoreceptors, rods and cones. While cones allow daytime vision and the perception of color and detail, cones rods are adapted for night vision and produce low resolution images in white and black.

Parts of the eye and their functions

The eyes work in a similar way to cameras.

The lens adjusts according to the distance of the stimulus, serving as a kind of lens that allows the refraction of light; The pupil is the diaphragm through which the image enters the eye and is projected onto the retina, from where it will be sent to the brain through the optic nerve.

1. Cornea

The cornea is the front part of the eye and is in contact with the outside. It is a transparent structure that covers the iris and lens and allows light refraction. Tears and aqueous humor allow the cornea to function properly, since they perform functions equivalent to those of blood.

2. Iris

This structure separates the anterior and posterior chambers of the eye. The dilator muscle of the iris increases the size of the pupil (mydriasis) and the sphincter muscle reduces it (miosis). Iris tissue is pigmented due to the presence of melanin; this gives rise to the color of the eye, by which we can easily identify this structure.

3. Pupil

There is a circular hole in the center of the iris that allows regulate the amount of light entering the eye when changing in size as a result of mydriasis and miosis; This opening is the pupil, the dark part that is located in the center of the iris.

4. Crystalline

The crystalline lens is the "lens" that sits behind the iris and allows visual focus. Accommodation is the process by which the curvature and thickness of the lens are modified to focus on objects based on their distance. When light rays pass through the lens, an image is formed on the retina.

5. Aqueous humor

Aqueous humor is found in the anterior chamber of the eyeball, between the cornea and the lens. It nurtures these two structures and allows eye pressure to remain constant. This liquid is made up of water, glucose, vitamin C, proteins, and lactic acid.

6. Sclera

Sclera covers the eyeball, giving it its characteristic white color and protecting internal structures. The anterior part of the sclera is attached to the cornea, while the posterior part has an opening that allows the connection between the optic nerve and the retina.

7. Conjunctiva

This membrane lines the sclera. Contributes to lubrication and disinfection of the eyeball since it produces tears and mucus, although the lacrimal glands are more relevant in this regard.

8. Choroid

We call the choroid layer of blood vessels and connective tissue that separates the retina and the sclera. The choroid provides the retina with the nutrients and oxygen it needs to function properly, in addition to maintaining a constant temperature in the eye.

9. Vitreous humor

The posterior chamber of the eye, which lies between the lens and the retina, is filled with vitreous humor, a gelatinous liquid with a density greater than that of aqueous humor of the anterior chamber. It constitutes most of the eyeball and its functions are to provide it with rigidity, cushion impacts, maintain intraocular pressure and fix the retina.

10. Retina

The retina is the true receptor organ of the visual system since the rods and cones, the photoreceptor cells, are located in this structure. This membrane lines the back of the eye and has a function similar to that of a screen: the lens projects the perceived images on the retina, from where it will be transmitted to the brain through the nerve optical.

Specifically, the rays of light are received by the area of ​​the retina known as the fovea, which, being very rich in cones, has great visual acuity and therefore is the main person in charge of detailed vision.

11. Optic nerve

The optic nerve is the second of the twelve cranial nerves. It is a set of fibers that transmit light impulses from the retina to the optic chiasm of the brain. From this point the visual information is sent to other areas of the brain in the form of electrical signals.

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