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The structure of human eyes
The structure of human eyes
Anonim

Human anatomy is one of the hardest questions people have been looking for answers to for millennia. The need to study the human body is obvious - the more we know about our body, the easier it is for us to keep it healthy or treat it in case of problems.

However, our body is one of the most mysterious mechanisms in nature.

Every year more and more incredible discoveries are made by scientists. The mechanisms that are found in the human body are striking in their complexity and accuracy. One of these most complex and unique mechanisms is vision. External work (image perception) is performed by the eye.

To understand how the process of forming a "picture" takes place, it is necessary not only to understand the structure of the eye, but also to be aware of how the information received from the outside is processed in the brain, and how the process of vision works in general.

The structure of the human eye

The human body is a very complex system of interconnected elements. Each organ performs a huge number of functions and has a complex structure. Only when the precise mechanism called "organism" works harmoniously does a person feel healthy. Every, even the most insignificant, flaw is a threat to the whole body. Every organ, even the smallest one, is vital. Nothing in this ideal system is superfluous.

Description of the structure of the eye

The human eyeball is shaped like a ball. The outer dense shell is called protein. Behind the protein is the bloodstream. It contains the vessels that feed the eye with blood. Outside, the albuminous membrane is covered with a transparent "film" - the cornea. The circulatory system in the front of the eye becomes iridescent. The color of the eyes depends on its color.

The black circle that we see in front of the eye is the pupil. Through it, light enters the eye. Behind it is a biconvex lens. The epithelium is adjacent to the choroid, staining it black. The inside of the eye is called the retina. The eye cavity is filled with a watery substance - the vitreous body (its structure resembles a gel).

Protein shell

This is a kind of protective layer of the eye. It prevents foreign microorganisms from entering the eye. It also protects against chemical damage. According to the structure diagram, the cornea, the outer convex part of the shell, resembles glass in a watch, covering the outer part of the eye. There are no blood vessels in it, it is absolutely transparent.

A huge number of nerve endings are concentrated in it, so it is sensitive to temperature and touch. Painful sensations arising from steam, cilia getting into the eye, etc. - this is the reaction of the cornea. In general, the cornea has a very complex structure.

It consists of five layers:

  • Anterior epithelium
  • Anterior boundary membrane
  • The main substance of the cornea
  • Posterior boundary membrane
  • Posterior epithelium

The top layer of the cornea is easily repaired, and problems associated with this particular layer of tissue are very rare. It provides hydration to the eye.

The anterior boundary membrane is a fairly dense layer, the meaning of which has not yet been determined.

Scientists have not come to a single conclusion regarding the functions of this layer. Many mammals do without it. This layer is the least recoverable.

Circulatory membrane

This membrane consists of many vessels that are responsible for nourishing the eyeball. Its inner side is painted with black pigment. It is a unique element in the human eye. Quite simply, it is responsible for the clarity of the image that we see. Light entering through the pupil creates a clear "picture". Light entering through the protein and iris would be redundant and vision would be blurry. The black pigment absorbs this extra light, ensuring normal vision.

Iris

The front of the choroid (what we see when looking into the eyes) is the iris. As you know, the color of the eyes is different for all people, and so the pigment melanin provides these differences. The color of the eyes depends on its amount in the iris.

In the middle of the iris is the pupil. As mentioned above, it absorbs light. Its diameter depends on the lighting, so in a darker room the pupil expands to "let in" more light to the retina. In bright light, it narrows because excess light would harm the retina of the eye.

Expansion and contraction occurs at the expense of the ciliary muscle. It is also a constituent part of the circulatory membrane. It is made up of several muscle cell systems. One system expands, the other narrows. A person does not even know about these micro movements in the eyes, but the quality of vision depends on them.

Lens

The lens is located behind the pupil. Its main function is to refract light. It also allows you to focus your gaze on objects of different distances. The lens has a biconvex shape. Its structure is also quite complex. The lens substance is enclosed in a capsule.

The anterior part of the capsule is covered from the inside with a layer of epithelium (the posterior part of the epithelium is devoid of it). The lens is attached with thin threads to the ciliary body. The lens is devoid of nerve endings and blood vessels. Thanks to this, it became possible to treat various problems associated with the lens through surgery. A transplant is done and the natural lens is replaced with an artificial one. In addition to the functions that directly provide vision, the lens acts as a natural barrier, preventing the vitreous from entering the front of the eye.

Retina

This is perhaps the most important part of the eyeball. It is she who provides us with vision. Its structure is very complex. A variety of cells react to light, thanks to this they distinguish objects, their shape and color, send signals to the brain and we, unaware of the most complex process taking place in our eyes, see the world around us.

That is why people are unable to see in the dark. The retina of the eye reacts to light. However, there are cells that react to low light (rods). Thanks to them, in very dimly lit places, we distinguish the contours of objects.

The structure and function of the retina are very complex. It is already difficult to imagine that cells must convert light into a nerve impulse that will go straight to the brain, and if you think about how fast this process takes place, vision becomes a real miracle.

The main elements of the retina:

  • Optic nerve
  • Vessels
  • Yellow spot

The optic nerve is a complex and vital element for vision. It is like a wire connected to the retina on the one hand and to the visual analyzer on the other. The visual analyzer is a part of the brain that continuously "decodes" the impulses sent by the retinal cells, transforming them into the visual images we are accustomed to.

This nerve consists of millions of fibers. Each of them provides specific areas of the image. If even one of these fibers fails, part of the "picture" will fall out. If the central nerve dies completely, the person will go blind irrevocably.

The macula is the place where the largest number of "cones" are concentrated. These are cells that allow you to see in the light. The above mentioned "rods" are located outside the macula, and the further from the macula, the fewer "cones" and more "rods".

There are also two chambers with aqueous humor in the eyes. They provide hydration and nutrition to all parts of the eyeball. The violation of moisture outflow leads to one of the most common eye diseases - glaucoma. Due to an excess of moisture, eye pressure can also rise. If there is a strong pressure drop, the optic nerve dies off and the person irrevocably becomes blind.

The presence of two eyes in a person allows us to see three-dimensionally and orient ourselves in space. Different impulses come from different "corners" of the eye, which are "glued" into a single image in the visual analyzer. Of course, a person's peripheral vision is not perfect, and what we see "out of the corner" of the eye is blurry, but this allows us to orient ourselves in space.

The outer part of the human eye is the eyelid. This is a muscle formation, covered with epithelium from the outside, and from the inside, it is a mucous membrane. The eyelid is obviously protective. As soon as there is a threat of mechanical damage to the eyeball, the person reflexively closes the eyelids. From the inside, the mucous membrane moisturizes the eye. Eyelashes are located along the edge of the eyelid, which also do not allow microelements to settle on the mucous membrane of the eye.

Also, speaking about the structure of the eye, it would be wrong not to mark the lacrimal glands and canals. The gland is located above the outer corner of the eye, and the lacrimal canals at the inner corner. Thanks to the tear fluid, the eye is moisturized. Tears also play an important role in protecting vision. When dust or another trace element enters the eye, tears immediately appear, which wash away foreign elements from the mucous membrane, thereby clearing the eye and preventing damage.

This is an incomplete and incomplete explanation of how human vision works and works. As you can see, this is a very complex multi-level process.

Hundreds of elements are interconnected and perform their functions. As soon as one of them breaks the chain, the person loses his sight, which means he loses visual connection with the world.

Vision, like any other process in the body, wears out, and therefore requires care and attention. You should be attentive to the health of your eyes, so as not to lose the joy of contemplating the environment over the years.

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