One of the most interesting topics in biology, in particular in human anatomy, is the structure of the eye. Since ancient times, many beliefs, legends and myths have been associated with the eyes. There are many sayings, of which the most famous is: “The eyes are the mirror of the soul.” But what is an eye, really? What can scientists tell about it? Ophthalmologists and biologists, anatomists, who have long been fascinated by the human system of vision, have found that the eye, despite its small size, has a very complex device. What - read on.
Sight is hard
The eye apparatus in anatomy is called stereoscopic. In the human body, he is responsible for ensuring that information is perceived correctly, correctly, without distortion. Through vision, data is processed and then transmitted to the brain.
Data about the object on the right is transmitted to the brain through the retinal element located on the right. The optic nerve is also involved in this process. But what is on the left perceives and studies the left side of the retina. The human brain is designed in such a way that it combines the information received without distortion, thereby forming a complete picture of the world around the beholder.
Eye structureprovides binocular vision. The eyes form a very complex system in their device. It is due to it that a person is able to perceive, process data received from the outside world. One of the basic concepts for this system is electromagnetic radiation. Human vision is based on it.
How does it work?
If you study the diagram of the human eye, you will notice that the organ as a whole is like a ball. This is what led to the name "apple". The structure of the eyes is the inside and three successive outer layers:
- outer;
- vascular;
- retina.
Sheaths of the eye
So, what is the structure of the eye outside? The uppermost part is called the "cornea". It is a fabric that can be compared to a window that opens a view of the world around. It is through the cornea that light enters the visual system. Since the cornea is convex, it is able not only to transmit light rays, but to refract them. The rest of the outside of the eye is called the sclera. It is an insurmountable barrier to light. Visually, the sclera looks like a boiled egg.
The next part included in the so-called light-sensitive structures of the eye is called the choroid. As the name already implies, it is formed by vessels through which oxygen and other necessary components and substances enter the tissues through the blood. The shell has several components:
- iris;
- ciliary body;
- choroid.
It so happened that peoplepay attention to the color of the interlocutor's eyes. What it will be is determined by the optical structure of the eye, namely the iris: a specific pigment accumulates in it. Since the cornea allows you to see the iris of another person, you can determine what color the eyes of the person you meet.
The pupil is located exactly in the center of the iris. It has a round shape, and changes dimensions, focusing on the level of lighting. In addition, various factors (such as taking medication) affect pupil dilation.
Moving deeper
If you look behind the iris, you can see the anterior chamber. It is here that the mechanisms by which intraocular fluid is produced are located. This substance circulates in the eye, washing its components. In the corner of the chamber there is a drainage system provided by nature, through which the liquid flows away from the eye. And in the depths of the ciliary body, you can find an accommodation muscle. Thanks to its functioning, the shape of the lens changes.
Even deeper is the choroid. The structure of the human eye suggests the presence of a posterior part in the choroid, and it is she who bears this beautiful and sonorous name. The choroid is in constant contact with the retina, which is necessary for proper tissue nutrition.
Third shell
Since it was mentioned above that the structure of the eyes involves three shells, it is necessary to talk about the retina. As its name implies, it is a mesh shell. It is formed by nerve cells. Fabric lines the eyeon the inner surface and guarantees high-quality vision if he althy.
The structure of the retina is such that an image received from the outside world is projected here. But different parts of the tissue function differently. The maximum ability to see is provided by the macula, that is, the center. This is due to the high density of visual cones. The data received by the retina is transmitted to a special nerve, through which it enters the brain, where it is promptly processed.
What's inside?
What is the structure of the human eye if you look under all three shells? Two cameras can be found here:
- front;
- rear.
Both of them are filled with a special liquid. In addition, here are:
- crystalline lens;
- vitreous body.
The first one is shaped like a lens convex on both sides. It is able to refract the light flux and transmit it. Thanks to the work of the lens, it becomes possible to focus the image on the retinal nervous tissue. But the vitreous body is most like jelly. Its main task is to prevent contact between the fundus and the lens.
Fibrous and conjunctival membranes
Studying the location of the structure of the eye, start with the conjunctiva. It is a transparent tissue on the outside of the eye. It is she who covers the eyelids from the inside. Thanks to the conjunctiva, the eyeballs can glide correctly without damage.
Speaking about the functions of the structures of the eye, one should not lose sight of the fibrous membrane. It is partly created from the sclera andhas a high density, which guarantees the protection of fragile internal contents. This fabric is supportive but transparent from the front, similar to the glass on a watch. This segment of the fibrous membrane is commonly referred to as the cornea.
The transparent part of the shell is rich in nerve cells, which guarantees the transmission of information. In the place where the sclera passes into the cornea, a limbus is isolated. This term is commonly understood as a zone of concentration of stem cells. Thanks to them, the outer part of the eye can regenerate in a timely manner.
Eye cameras
The anterior chamber is located between the iris and the cornea, in particular, its angle, and the drainage system mentioned above. Analyzing the location of the shells and structures of the eye, a little further inward you can see the lens. So that it does not move from an anatomically correct position, thin ligaments are provided by nature. They attach the organ to the ciliary body.
The front and back chambers are full of colorless moisture. This fluid nourishes the lens, supplies the nutrients necessary for the functioning of the cornea. This is important because these elements of the human vision system do not have their own blood supply.
Optics is a complex structure
Human vision is provided by the fact that there are refractive structures of the eye. It is due to the complex optics of the visual system that data from the environment can be perceived. The perception of the space around oneself will be correct if all organs and tissues function normally in a person:
- auxiliary structures of the eye;
- light-conducting;
- receptive.
When working correctly, you can be sure of the clarity of vision.
Key elements of the optical system:
- cornea;
- crystalline lens.
Please note that the light-refracting structures of the eye include both the vitreous body and the moisture contained in the chambers of the eye. Therefore, vision will be good only if they:
- transparent;
- do not contain blood;
- have no haze.
Only when the rays of light pass through this system, they are on the retina, where the formation of the image of the surrounding space. Remember that it manifests:
- upside down;
- reduced.
In this case, nerve impulses are formed that enter the nerve and are transmitted through it to the brain. Neurons analyze the information received, thanks to which a person gets a detailed idea of \u200b\u200bwhat surrounds him.
The cornea is a complex element of the eye system
The photosensitive structures of the eye include various elements, not least of which is the cornea. It is formed by five types of fabrics:
- epithelium in front;
- Reichert record;
- stroma;
- Descemet fabric;
- endothelium.
Despite having five components, the cornea is only about a millimeter thick. Please note that although the light-refracting structures of the eyerelatively large, the cornea is only a fifth of the fibrous membrane, that is, it is a tiny element of a complex complex.
The cornea is about 11 mm vertically, and only a millimeter larger in width. The specificity of the structure of the organ ensures its transparency: the cells that form the tissue are built according to a strictly structured scheme. Another tool used by nature in creating the cornea is the exclusion of blood vessels. But there are a lot of nerve endings here. The refractive structures of the eye include several tissues, but this organ is characterized by a high refractive power, and it is one of the main ones.
Ciliary body
The light-sensitive structures of the eye also include the components that make up the ciliary body. It is part of the choroid, representing its middle part, somewhat larger in thickness than other elements. Visually, the ciliary body is similar to a circular roller. Conventionally, scientists divide it into two elements:
- vascular, i.e. formed by blood vessels;
- muscular, created by the ciliary muscle.
The first component combines about 70 thin processes capable of producing fluid that provides nourishment and cleansing of the eye structure. Zinn ligaments also come from here, thanks to which the lens is firmly fixed in its proper place.
The retina as one of the key elements of visualsystems
This tissue in anatomy is classified as an element of the visual analyzer. Its key feature is the ability to convert light impulses into nerve impulses, which are then processed by the human body.
The retina contains six layers:
- Pigment (aka external). This element is capable of absorbing light, thereby greatly reducing the scattering phenomenon inside the eye.
- Processes of cells. Scientists call them flasks and sticks. Rhodopsin and iodopsin are formed in the processes.
- The fundus of the eye. It is an active element of the visual system. When examining the eye, it is the ophthalmologist who sees it.
- Vascular layer.
- The disc of the nerve, marking the point where the nerve leaves the eye.
- Yellow spot, which is commonly understood as the area of tissue where the density of cones is highest, providing the possibility of color vision of the surrounding space.
What kind of liquid?
Above, the intraocular fluid that fills the chambers, which is mandatory for the normal functioning of the eye, has been mentioned more than once. Visually and in its structure, it is most like pure water. But the composition of the eye fluid is similar to blood plasma. It provides proper nutrition.
How is the eye protected?
Considering such a delicate and fragile structure, one cannot ignore the protective mechanisms provided by nature. The highest level of protection is the eye socket. It is a bone container. If you examine the eyevisually, it will become clear that it is similar to a four-sided pyramid, but as if truncated. The top of the pyramid looks into the skull. Tilt angle - 45 degrees. The depth of the human eye socket is from 4 to 5 cm.
Please note: the eye socket is indeed larger than the eyeball. This is necessary so that the fat body can also fit here, as well as the nerve and muscles, the vascular system, which ensures the correct functioning of the eye.
The eyelids are also part of the structure of the eye
In a normal he althy human body, each eye is protected by two eyelids:
- bottom;
- top.
They help keep the fragile system safe from outside objects. The closing of the eyelids occurs unconsciously, the reaction is instantaneous not only in case of serious danger, but even when the wind is blowing. The eyelids protect the eye when touched.
Blinking movements help clear the cornea of dust components. Thanks to them, tear fluid is evenly distributed. Also, the eyelids are equipped with eyelashes growing on the edges. In our time, they have become an important element of ideas about human beauty, but nature is conceived primarily to protect the visual system. Eyelashes protect the eye from dust and small debris that could damage delicate fabrics.
The human eyelids are a fairly thin layer of skin that forms wrinkles. Under the epithelium is the muscle layer:
- circular, providing closure;
- lifting the eyelid from above.
But the inner side, as already mentioned, is lined with conjunctiva.
How do tears form?
Many signs, traditions, even ways of thinking are associated with tears in human culture. The classic idea that has developed over many centuries: "Severe men do not cry", "It's shameful to cry!". Is it true that tears are only an indicator of a person’s mental weakness? Nature, in creating the lacrimal apparatus, sought to ensure the protection and correct functioning of the visual system, so in fact even men can afford to cry, thereby cleansing and protecting their eyes.
Tears are such transparent drops of a specific liquid, which are characterized by weak alkalinity. The composition of tears is very complex, but the key ingredient is pure water. Normal excretion per day is about a milliliter. Tears protect the eyes and help nourish tissues and help you see better.
Lacrimal apparatus includes:
- the gland that produces tears;
- points of tears;
- channels;
- bag;
- duct.
The gland is located in the orbit, in the upper part of its wall, outside. It is here that tears are formed, which then fall into the channels intended for this, and from there to the ocular surface. Excess moisture moves down, where the conjunctival fornix is provided for this.
There are two lacrimal openings: above and below. Both of them are in the inner corner, on the ribs of the eyelids. Through them, teardrops pass through the channels into the sac close to the wing of the nose, then directly into the nose.
How many muscles in the eye system?
Ifto study the muscular apparatus, it will become clear that six muscles function in the human eye. They are divided into the following groups:
- oblique;
- straight.
The first are subdivided into:
- lower;
- top.
The straight lines are the remaining four, which are known to science under the names:
- lower;
- top;
- central;
- lateral.
In addition, the eye system includes the above-mentioned mechanisms for lifting the upper eyelid and closing eyes.
Diseases associated with disorders of the eye structure
So it turns out that people suffer from eye diseases at all ages. Eye problems haunt people regardless of their social status, we alth, living conditions, nationality. However, in some cases, we can talk about a predisposition associated with genetics, ecology or other factors. Usually eye disorders are provoked by:
- incorrect arrangement of one or another element of the structure;
- a defect in part of the eye.
Distinguish diseases:
- provoking a decrease in severity;
- pathological functional disorders.
From the first group are often found:
- myopia;
- farsightedness;
- astigmatism.
The second group includes:
- glaucoma;
- cataract;
- strabismus;
- anophthalmos;
- retinal detachment;
- myodesopsia.
Most often found inrecent nearsightedness and farsightedness. In the first case, the eyeball is characterized by a length that exceeds the norm. Due to this deformation, the light is focused without reaching the retina. Because of this, a person loses the ability to clearly see the world around him, especially objects in the distance. Usually prescribe glasses with negative diopters.
For farsightedness is characterized by the reverse picture. The reason for the violation is that the lens becomes inelastic or the eyeball decreases in length. Accommodation weakens, the rays are already focused behind the retina, and the person cannot clearly distinguish those objects that are nearby. In this case, glasses with positive diopters are prescribed.
Please note: glasses should be prescribed only by an ophthalmologist, it is unacceptable to prescribe lenses or glasses yourself. When selecting, the eyes are measured, the distance between the pupils is calculated and the fundus is carefully checked, as well as the extent of violations is identified. When analyzing all the data received, the doctor recommends choosing certain glasses, and may also advise you to have an operation or otherwise correct your vision.
But astigmatism is much less common. With this disorder, the brain cannot receive correct information about the surrounding space due to a defect in the lens, the cornea, which leads to the fact that the eye shell loses the shape of a sphere.
