The 11 parts of the eye and their functions

We explain the different components of the eyeball, their characteristics and functions.

Vision stands out among human sensory-perceptual systems for 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 come to be used as a supposedly irrefutable argument by those who defend that life was created and designed by a god.

The analysis of the parts of the eye can be greatly extended since the organs of vision are composed of many structures. In this article we will focus on the main ones and on the general description of the transduction process that causes light energy to be perceived as images.

What is the eye?

The eyes are the basis of the visual system. These organs transforms light energy into electrical impulses which, when transmitted to the visual cortex of the occipital lobe, enable 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, filled respectively with aqueous humor and vitreous, liquids that regulate intraocular pressure. The anterior chamber is smaller and is located between the cornea and the iris, while the posterior chamber is composed of the other parts of the eye.

Unlike other sensory organs, the eye is partially derived from the central nervous system. 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 cerebral hemispheres, the thalamus and the hypothalamus.

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

Parts of the eye and their functions

Eyes function similarly to cameras.

The crystalline lens adjusts according to the distance of the stimulus, serving as a sort 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 constitutes the anterior part of the eye and is in contact with the exterior. It is a transparent structure that covers the iris and the crystalline lens and allows light refraction. 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). The iris tissue is pigmented due to the presence of melanin; this gives rise to the color of the eye.This gives rise to the color of the eye, by which we can easily identify this structure.

3. Pupil

There is a circular orifice in the center of the iris that allows to regulates the amount of light that enters the eye by changing by changing size as a result of mydriasis and miosis; this opening is the pupil, the dark part located in the center of the iris.

4. Crystalline lens

The crystalline lens is the "lens" that lies 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 as a function of their distance. to focus on objects as a function of their distance. When light rays pass through the lens, the image is formed on the retina.

5. Aqueous humor

The aqueous humor is found in the anterior chamber of the eyeball, between the cornea and the crystalline lens. It nourishes these two structures and allows the pressure in the eye to remain constant.. This fluid is composed of water, glucose, vitamin C, proteins and lactic acid.

6. Sclera

The sclera covers the eyeball, giving it its characteristic white color and protecting the internal structures. and protecting the 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. It contributes to the lubrication and disinfection of the eyeball by producing tears and mucus. as it produces tears and mucus, although the lacrimal glands are more relevant in this regard.

8. Choroid

We call the "choroid" the layer of Blood vessels and tissue layer of blood vessels and connective tissue that separates the retina that separates the retina and the sclera. The choroid provides the retina with the nutrients and oxygen it needs to function properly, as well as 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 fluid with a higher density than the aqueous humor in the anterior chamber. of the anterior chamber. It makes up most of the eyeball and its functions are to stiffen the eye, cushion impact, maintain intraocular pressure and fix the retina.

10. Retina

The retina is the actual receptor organ of the visual system because the rods and cones, the photoreceptor cells, are located in this structure. This membrane covers the back of the eye and has a function similar to that of a screen: the lens projects the perceived images onto the retina, from where they will be transmitted to the brain through the optic nerve.

Specifically, the light rays are received by the area of the retina known as the fovea, which, being very rich in contrasts, is the most important part of the retina.This area, which is very rich in cones, has a great visual acuity and is therefore the main responsible for detail vision.

11. Optic nerve

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