Vision differs from human sensory systems by its great 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 compelling argument by those who hold that life was created and designed by a god. .
Analysis of parts of the eye it can spread to a large extent because the organs of vision are made up of many structures. In this article, we will focus on the main ones and 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 they transform light energy into electrical impulses which, when transmitted to the visual cortex of the occipital lobe, enables three-dimensional perception of shape, movement, color and depth.
Eyeballs are spherical in shape and approximately 2.5 cm in diameter. They are divided into two sections: the anterior and posterior chamber, respectively filled with aqueous humor and vitreous, liquids that regulate intraocular pressure. The anterior chamber is smaller and sits between the cornea and the iris, while the posterior chamber is made up of the rest of the eye.
Unlike other sense organs, the eye it 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, rods and cones. While the cones allow day vision, color perception and detail, the rods are suitable for night vision and produce low resolution black and white images.
Parts of the eye and their functions
Eyes work the same way as cameras.
The lens adjusts 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 into the retina, from where it will be sent to the brain via the optic nerve.
The cornea forms the anterior part of the eye and is in contact with the outside. It is a transparent structure that covers the iris and the lens and allows the refraction of light. Tears and aqueous humor allow the cornea to function properly, as they perform functions equivalent to those of blood.
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 decreases it (mydriasis). Iris tissue it is pigmented due to the presence of melanin; this is reflected in the color of the eyes, thanks to which we can easily identify this structure.
There is a circular hole in the center of the iris which allows regulate the amount of light entering the eye when resizing as a result of mydriasis and miosis; this opening is the pupil, the dark part that is located in the center of the iris.
The lens is the “lens” that sits behind the iris and provides visual focus. Accommodation is the process by which the curvature and thickness of the lens is changed by focus on objects based on their distance. When light rays pass through the lens, the image forms in the retina.
5. Aqueous humor
Aqueous humor is found in the anterior chamber of the eyeball, between the cornea and the lens. It nourishes these two structures and keeps eye pressure constant. This liquid is made up of water, glucose, vitamin C, protein and lactic acid.
The sclera it covers the eyeball, giving it its characteristic white color and the protection of internal structures. The anterior part of the sclera is attached to the cornea, while the posterior part has an opening that allows connection between the optic nerve and the retina.
This membrane covers the sclera. It contributes to the lubrication and disinfection of the eyeball as it produces tears and mucus, although the tear glands are more relevant in this regard.
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, in addition to maintaining a constant temperature in the eye.
9. Vitri humor
The posterior chamber of the eye, located between the lens and the retina, is full of vitreous humor. gelatinous fluid of higher density than aqueous humor from the previous bedroom. It constitutes the major part of the eyeball and its function is to give it rigidity, absorb shocks, maintain intraocular pressure and fix the retina.
The retina is the true receptor organ of the visual system since in this structure are the rods and cones, the photoreceptor cells. This membrane covers the back of the eye and has a function similar to that of a screen: the lens projects the perceived images into the retina, from where they will be transmitted to the brain by the optic nerve.
More precisely, the rays of light they are received by the area of the retina known as the fovea, Which, being very rich in cones, has great visual acuity and is therefore primarily responsible for seeing details.
11. Optic nerve
The optic nerve is the second of the twelve cranial pairs. It is a set of fibers that transmit light pulses from the retina to the cerebral optic chiasm. From this point, visual information is sent to other areas of the brain in the form of electrical signals.