The human eye is a very complex optical system, consisting of a variety of elements, each of which is responsible for its own tasks. In general, the eye apparatus helps to perceive an external image, process it and transmit information in an already prepared form to the brain. Without its functions, the organs of the human body could not interact as fully. Although the organ of vision is complex, every person should understand at least a basic description of the principle of its functioning.
Having understood what the eye is and understanding its description, let’s consider the principle of its operation. The eye works by perceiving light reflected from surrounding objects. This light hits the cornea, a special lens that allows the incoming rays to be focused. After the cornea, the rays pass through the chamber of the eye (which is filled with a colorless liquid), and then fall on the iris, which has a pupil in its center. The pupil has a hole ( palpebral fissure), through which only the central rays pass, that is, part of the rays located at the edges of the light flux are eliminated.
The pupil helps adapt to different levels of light. It (more precisely, its palpebral fissure) filters out only those rays that do not affect the quality of the image, but regulates their flow. As a result, what is left goes to the lens, which, like the cornea, is a lens, but only intended for something else - for more accurate, “finish” focusing of light. The lens and cornea are the optical media of the eye.
Next, the light passes through a special vitreous body, which enters the optical apparatus of the eye, onto the retina, where the image is projected like on a movie screen, but only upside down. In the center of the retina there is the macula, the zone that responds to the object that we look at directly.
During the final stages of image acquisition, retinal cells process what is on them, translating everything into electromagnetic impulses, which are then sent to the brain. A digital camera functions in a similar way.
Of all the elements of the eye, only the sclera, a special opaque membrane that covers the outside, does not participate in signal processing. It surrounds it almost entirely, approximately 80%; in the anterior part it smoothly passes into the cornea. Among the people outer part It is usually called a protein, although this is not entirely correct.
The human organ of vision perceives images in color, and the number of shades of colors that it can distinguish is very large. How much different colors differs by eye (more precisely, how many shades), can vary from the individual characteristics of a person, as well as the level of his training and the type of his professional activity. The eye “works” with the so-called visible radiation, which represents electromagnetic waves, having a wavelength from 380 to 740 nm, that is, with light.
If we take average indicators, then a person can distinguish about 150 thousand color tones and shades in total.
However, there is an ambiguity here, which lies in the relative subjectivity of color perception. Therefore, some scientists agree on another figure for how many shades of colors a person usually sees/distinguishes – from seven to ten million. In any case, the figure is impressive. All these shades are obtained by varying the seven primary colors found in different parts rainbow spectrum. It is believed that professional artists and designers have a higher number of perceived shades, and sometimes a person is born with a mutation that allows him to see many times more colors and shades. How many different colors such people see is an open question.
Like any other system human body, the organ of vision is susceptible to various diseases and pathologies. Conventionally, they can be divided into infectious and non-infectious. Common types of diseases that are caused by bacteria, viruses or microorganisms are conjunctivitis, stye and blepharitis.
If the disease is non-infectious, it usually occurs due to severe eye fatigue, due to hereditary predisposition or simply due to changes that occur in the human body with age. Less commonly, the problem may be that a general pathology of the body has arisen, for example, hypertension has developed or diabetes mellitus. As a result, glaucoma, cataracts or dry eye syndrome may occur, and the person ultimately sees or distinguishes objects worse.
IN medical practice All diseases are divided into the following categories:
To avoid problems and pathologies, the eyes must be protected, not kept pointed at one point for a long time, and optimal lighting maintained when reading or working. Then the power of vision will not decrease.
The human eye has not only internal structure, but also the external, which is represented by centuries. These are special partitions that protect the eyes from injury and negative factors environment. They mainly consist of muscle tissue, which is covered on the outside with thin and delicate skin. In ophthalmology, it is generally accepted that the eyelids are one of the essential elements, which can cause problems if problems arise.
Although the eyelid is soft, its strength and consistency of shape are ensured by cartilage, which is essentially a collagen formation. The movement of the eyelids is carried out thanks to the muscle layer. When the eyelids close, this has a functional role - the eyeball is moistened, and small foreign particles, no matter how many there are on the surface of the eye, are removed. In addition, due to the wetting of the eyeball, the eyelid is able to slide freely relative to its surface.
An important component of the eyelids is also an extensive blood supply system and many nerve endings that help the eyelids carry out their functions.
Human eyes move with special muscles, providing the eyes with normal constant functioning. The visual apparatus moves with the help of the coordinated work of dozens of muscles, the main of which are four straight and two oblique muscle processes. surround from different sides and help rotate the eyeball around different axes. Each group allows you to turn a person’s eye in its own direction.
The muscles also help lift and lower the eyelids. When all the muscles work harmoniously, this not only allows you to control the eyes individually, but also to carry out their harmonious work and coordination of their direction.
Human eye- This is a paired organ that provides the function of vision. The properties of the eye are divided into physiological And optical, therefore they are studied by physiological optics - a science located at the intersection of biology and physics.
The eye is shaped like a ball, which is why it is called eyeball.
The skull has eye socket– location of the eyeball. A significant part of its surface is protected there from damage.
Oculomotor muscles provide motor ability of the eyeball. Constant hydration of the eye, creating a thin protective film, is provided by the lacrimal glands.
Structure of the human eye - diagram
The information the eye receives is light, reflected from objects. The final stage is information entering the brain, which actually “sees” the object. Between them is eye- an incomprehensible miracle created by nature.
Photo with description
The first surface that light hits is . This is a “lens” that refracts the incident light. Parts of various optical instruments, such as cameras, are designed like this natural masterpiece. The cornea, which has a spherical surface, focuses all rays at one point.
But before the final stage, light rays have to go a long way:
This is the internal structure of the eye and the path of light flow inside it.
Video:
The eyeball has three membranes: 
Compound:
2. Vascular the membrane of the eye - its structure and functions can be seen in the figure above. It is the middle “layer”. Blood vessels, present in it, provide blood supply and nutrition.
Composition of the choroid:
It has several layers that provide different functions, the main one of which is light perception.
Contains sticks And cones – photosensitive receptors. Receptors function differently depending on the time of day or the lighting in the room. Night is the time of rods; during the day, cones are activated.
Although the eyelids are not included visual organ, it makes sense to consider them only in aggregate.
Purpose and structure of the eyelid:
The eyelid consists of muscles covered with skin, with eyelashes on the edge.
The main goal is to protect the eye from aggressive external environment, as well as constant hydration.
Thanks to the presence of muscles, the eyelid can move easily. With regular closure of the upper and lower eyelids, the eyeball is moistened.
The eyelid consists of several elements:
One of the methods alternative medicine, based on the structure of the eye, is Iridology. The iris diagram helps the doctor make a diagnosis when various diseases in the body:
This analysis is based on the assumption that different organs and areas of the human body correspond to certain areas on the iris. If an organ is sick, this is reflected in the corresponding area. These changes can be used to determine the diagnosis.
The importance of vision in our lives cannot be overestimated. In order for it to continue to serve us, it is necessary to help it: wear glasses to correct vision, if required, and sunglasses in bright sunshine. It is important to understand what happens over time age-related changes which can only be delayed.
The human eye is a complex optical system consisting of many functional elements. Thanks to them coordinated work we perceive 90% of incoming information, that is, the quality of our life largely depends on vision. Knowing the structure of the eye will help us better understand how it works and the importance of the health of each element of its structure.
Many people remember how human eyes work from school. The main parts are the cornea, iris, pupil, lens, retina, macula and optic nerve. TO eyeball muscles are suitable, providing them with coordinated movement, and for a person - high-quality three-dimensional vision. How do all these elements interact with each other?
The eye structure resembles a powerful lens that collects rays of light. This function is performed by the cornea - the anterior transparent layer of the eye. Interestingly, its diameter increases from birth to 4 years, after which it does not change, although the apple itself continues to grow. This is why young children's eyes appear larger than adults'. Having passed through it, the light reaches the iris - the light-proof diaphragm of the eye, in the center of which there is a hole - the pupil. Thanks to its ability to contract and expand, our eye can quickly adapt to light of different intensities. From the pupil, rays fall on a biconvex lens - the lens. Its function is to refract rays and focus the image. The lens plays an important role as part of the light-refracting apparatus, since it is capable of adjusting to the vision of objects located at different distances from a person. This arrangement of the eye allows us to see well both near and far.
Many of us remember from school about such parts of the human eye as the cornea, pupil, iris, lens, retina, macula and optic nerve. What is their purpose?
From the pupil, rays of light reflected from objects are projected onto the retina of the eye. It represents a kind of screen on which the image of the surrounding world is “transmitted”. Interestingly, it is initially upside down. Thus, land and trees are transferred to top part retina, sun and clouds - on the bottom. What our gaze is currently directed at is projected onto the central part of the retina (fovea). It, in turn, is the center of the macula, or macula zone. It is this area of the eye that is responsible for clear central vision. Anatomical features The fovea determines its high resolution. A person has one central fovea, a hawk has two in each eye, and, for example, in cats it is represented by a long visual stripe. This is why the vision of some birds and animals is sharper than ours. Thanks to this device, our eyes clearly see even small objects and details, and also distinguish colors.
It is worth mentioning separately the photoreceptors of the retina - rods and cones. They help us see. Cones are responsible for color vision. They are mainly concentrated in the center of the retina. Their sensitivity threshold is higher than that of sticks. With the help of cones, we see colors provided there is sufficient lighting. Rods are also located in the retina, but their concentration is maximum at its periphery. These photoreceptors are active in dim lighting. It is thanks to them that we can distinguish objects in the dark, but we do not see their color, since the cones remain inactive.
In order for us to see the world “correctly”, the brain must connect to the work of the eye. Therefore, the information that was collected by the light-sensitive cells of the retina is transmitted to the optic nerve. To do this, it is converted into electrical impulses. By nerve tissues they are transmitted from the eye to the human brain. This is where the analysis work begins. The brain processes the incoming information, and we perceive the world as it is - the sun in the sky above, and the earth under our feet. To check this fact, you can put it on your eyes special glasses, which flip the image. After some time, the brain will adapt, and the person will again see the picture from his usual perspective.
As a result of the processes described, our eyes are able to see the world around us in all its fullness and brightness!
Vision and hearing are much better developed in humans than the sense of smell. Light-sensitive cells and cells that detect sounds are collected in us, like in all highly developed animals, in special organs - the eyes and ears.
Like a camera, our eye has a “lens window” (cornea), a diaphragm (iris), an “adjustable lens” (lens) and a light-sensitive layer (the retina, which lies deep in the eye). Retinal cells send signals along the optic nerve to the cerebral cortex.
There are two types of light-sensitive cells in the human eye: rods and cones. The rods distinguish between dark and light. Cones perceive color. Cells of both types are located on the retina, which is thin and riddled with blood vessels. inner shell eyeball. In general, the eyeball consists of several dense layers connective tissue that gives it its shape.
Thanks to the lens, everything we see is reflected upside down on the retina. However, the brain corrects the distorted picture. In general, he easily adapts to everything. If someone decides to stand on his head for weeks on end, soon instead of upside-down pictures he will again begin to see normal, “put on his feet” images.
1. Optic nerve; 2. Muscle; 3. Frontal bone; 4. Cornea; 5. Muscle
The front part of the eyeball - the cornea - is transparent, like glass: it transmits light into the eye. The light is then captured by the eye's "diaphragm" - the iris - and collected into a beam. Pigment cells in the iris give the eyes a certain color. If there is a lot of pigment, the eyes are colored brown, if there is little or none of it - in greenish-gray and blue tones. The light then enters the pupil, a hole in the iris surrounded by two small muscles. In bright light, one muscle constricts the pupil, the other dilates it if it is dark. Having passed the pupil, the light rays fall directly on the lens - an elastic organ that constantly tries to take the shape of a ball. A ring of muscles interferes with it: they constantly stretch and reduce the convexity of the lens. So, the lens easily changes its curvature. Therefore, light rays fall precisely on the layer of the retina dotted with rods and cones, and we clearly see objects. When we look at objects that are close to us, the lens becomes convex and refracts rays more strongly, and when objects are far away from us, it becomes flatter and refracts rays weaker. With age, the lens loses elasticity. In order to somehow fix the problem, we have to help our natural lens- lens - and use glasses.
Like a camera, the eye is equipped with a “lens window,” a “diaphragm,” an “adjustable lens,” and a “photosensitive layer,” which resembles photographic film. Only this layer is part of the eye itself, its retina. And yet a person sees more than a camera. After all, he looks at the world with two eyes. Both the left and right eyes see objects differently. Our brain compares the two images received and judges the shape of what we see. That's why people have spatial vision. But, for example, a chicken’s eyes are set on the sides of its head, and it is not endowed with three-dimensional vision.
Almost every third person suffers from visual impairment. Myopia and farsightedness are the most common, but can be corrected very well with glasses or contact lenses. Myopia occurs as a result of eye pathology. A nearsighted person can see clearly up close, but when looking into the distance, the image becomes very blurry. Farsightedness is a consequence of normal aging of the eye. Starting at the age of 40, we see up close less and less clearly, as over the years the lens loses its flexibility.
The structure of the human eye is practically no different from the structure of many animals. In particular, the eyes of humans and octopuses have the same anatomy.
The human organ of vision is incredibly complex system, including large number elements. And if its anatomy has been disturbed, then this becomes the cause of vision deterioration. In the worst case, it causes absolute blindness.
Diagram of the structure of the human eye:
The external structure of the eye is represented by the following elements:
The structure of the eyelid is quite complex. The eyelid protects the eye from the negativity of the environment, preventing accidental injury. Represented by muscle tissue, protected on the outside skin, and from the inside - the mucous membrane, which is called the conjunctiva. It is this that ensures eye hydration and unhindered movement of the eyelid. Its outer outer edge is covered with eyelashes that perform a protective function.
The lacrimal department is represented by:
Tears serve two functions:
The pupil occupies the center of the iris and is a round hole with a varying diameter (2 – 8 mm). Its expansion and contraction depends on the illumination and occurs automatically. It is through the pupil that light falls on the surface of the retina, which sends signals to the brain. The muscles of the iris are responsible for its work - expansion and contraction.
The cornea is represented by a completely transparent elastic membrane. It is responsible for maintaining the shape of the eye and is the main refractive medium. Anatomical structure The human cornea consists of several layers:
The sclera (white part) is the opaque outer layer of the eye. The lateral and posterior part of the eye is lined with the white surface, but in front it smoothly transforms into the cornea.
The structure of the sclera is represented by three layers:
It includes nerve endings and an extensive network of blood vessels. The muscles responsible for the movement of the eyeball are supported (attached) by the sclera.
The internal structure of the eye is no less complex and includes:
Internal structure of the human eye:
The lens is another important refractive medium of the eye. It is responsible for focusing the image on its retina. The structure of the lens is simple: it is a completely transparent biconvex lens with a diameter of 3.5–5 mm with variable curvature.
The vitreous body is the largest spherical formation, filled with a gel-like substance that contains water (98%), protein and salts. It is completely transparent.
The iris of the eye is located directly behind the cornea, surrounding the opening of the pupil. It has the shape of a regular circle and is penetrated by many blood vessels.
The iris can have different shades. The most common is brown. Green, gray and blue eyes are more rare. Iris blue color is a pathology and appeared as a result of a mutation about 10 thousand years ago. Therefore, all people with blue eyes single ancestor.
The anatomy of the iris is represented by several layers:
On its uneven surface there is a pattern characteristic of the eye of a particular person, created by pigmented cells.
The retina is one of the departments visual analyzer. The outer side is adjacent to the eyeball, and the inner side touches vitreous. The structure of the human retina is complex.
It has two parts:
The work of this part of the eye is to receive, process and transform the light flux into an encrypted signal about the resulting visual image.
The retina is made up of special cells - cones and rods. At poor lighting The rods are responsible for the clarity of the picture. The duty of cones is to transmit color. The eye of a newborn baby in the first weeks of life does not distinguish color, since the formation of the cone layer in children is completed only by the end of the second week.
The optic nerve is represented by many intertwined nerve fibers, including the central canal of the retina. Thickness optic nerve is approximately 2 mm.
Table of the structure of the human eye and description of the functions of a specific element:
The importance of vision for a person cannot be overestimated. We receive this gift of nature as very young children, and our main task is to preserve it for as long as possible.
We invite you to watch a short video tutorial on the structure of the human eye.
