Structure of the human eye and its functions

The structure of the human eye is very complex. What does the human eye consist of and what role do the various organs play? Discover the structure of the eye and its functions!

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1. Structure of the human eye

The eye consists of the eyeball, the optic nerve and additional organs such as the muscles of the eyeball, eyelid and the lacrimal organ. The eyeball, ie a sphere approximately 24 mm in diameter, has a weight of approximately 7 g and a volume of 6.5 cm³.

It is divided into three membranes. The first, the outer fibrous membrane, is the sclera and the cornea. Below it is the middle uveal, called the iris, the ciliary body, and the choroid. The third, inner membrane is called the retina.

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2. Structure of the eye and functions

2.1. Sclera

The sclera is made of elastic collagen fibers. It is the compact tissue of the eye and is responsible for the spherical shape of the eyeball. It has protective functions for the eye. It has three layers - the superficial epidural, the sclera proper (stroma), and the last layer is a brown plaque, adjacent to the uveal membrane and inside the eyeball.

The front sclera passes into the cornea.

2.2. Cornea

The cornea is the transparent part of the eye. It performs not only a protective function - thanks to it, the process of refracting the sun's rays in the eye takes place. This is done on the uneven surface that this part of the eye is made of. As the rays pass through the cornea, its protuberances cause the light to refract.

2.3. Iris and pupil

Immediately behind the cornea is the iris, which can be of different colors. This element of the eye is responsible for the color of our eyes.

In the center of the iris is the pupil - an opening that reacts to the amount of light, which means that it changes its width depending on its intensity. Thanks to this, it has the function of regulating the flow of light directly to the eye. Between the cornea and the iris is the anterior chamber filled with a clear liquid.

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2.4. Ciliary body

The iris turns into a ciliary body, similar in shape to a small ring (approx. 6–8 mm) inside the eye. Its task is to keep the lens in the right position.

The ciliary body has appendages (approx. 70–80) and a deeper, flat part. There are ligaments attached to the outgrowths, which allow the lens to be suspended.

2.5. Lens

The eye lens has a transparent and flexible structure. Due to its special structure, it can change shape, which means that it can both decrease and increase optical power.

This accommodation mechanism allows you to see objects closer and further away from the eye more sharply and clearly.

2.6. Vitreous body

The vitreous body is a gelatinous, transparent substance that fills the inside of the eyeball, and precisely the place behind the lens. The space between the lens and the cornea is filled with the aqueous fluid produced by the ciliary body. Both the aqueous humor and the vitreous body help shape the eyes.

2.7. Yellow dot

The most sensitive part of the retina is the macula, which concentrates the greatest number of photoreceptors: cones and rods. The suppositories are responsible for the perception of the colors and shapes of individual objects in bright light, and the purpose of the rods is to adjust the eye to seeing in dim and dark light.

Important processes also take place in the optic disc, which is why it is an essential part of the fundus - retinal arterial vessels exit and venous vessels enter.

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2.8. The muscles of the eyeball

The muscles of the eyeball are responsible for the correct movement of the eyeball. There are 6 of them in total - including four straight muscles (upper, lower, lateral and medial), as well as two oblique muscles (lower and upper).

Two-way rotation of the eyeball - right and left depend on the muscles: straight, medial and lateral. Upward rotational movements are performed by the upper rectus and lower oblique muscles, while the downward rotation is the result of the work of the lower rectus and upper oblique muscles. If any of the muscles mentioned is not working at full capacity, the eyes are set in strabismus.

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