One of the most interesting topics in biology, in particular in human anatomy, is the structure of the eyes. Since ancient times, it is with the eyes that many beliefs, legends and myths have been associated. There are many sayings, of which the most famous is: "Eyes are the mirror of the soul." But what is an eye really? What can scientists say about him? Ophthalmologists and biologists, anatomists, since ancient times carried away by the human vision system, have found that the eye, despite its small size, has a very complex structure. Which - read on.
Vision is not easy
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. Thanks to vision, data is processed and then transmitted to the brain.
Data about the object on the right to the brain is transmitted 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 holistic picture of the world around the beholder.
The structure of the eyes provides 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 pattern of the human eye, you will notice that the organ as a whole is like a ball. That is what caused him to be called the "apple." The structure of the eyes is the inside and three consecutive outer layers:
Shell of the eye
So, what is the structure of the eye outside? The upper part is called the "cornea". This is a fabric that can be compared with a window that opens a view of the surrounding world. It is through the cornea that light enters the visual system. Since the cornea is convex, it is able not only to let through the rays of light, but to refract them. The rest of the eye is called the sclera from the outside. It is an insurmountable barrier to light. Visually, the sclera looks like a boiled egg.
The next part, included in the so-called photosensitive structures of the eye, is called the choroid. As the name 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 people pay attention to the color of the eyes of the interlocutor. The way it will be determined by the optical structure of the eye, namely the iris: it accumulates a specific pigment. Since the cornea allows you to see the iris of another person, you can determine what color the eyes of the person you met.
The pupil is located exactly in the center of the iris. It has a round shape, and changes size, focusing on the level of lighting. In addition, various factors (for example, taking medication) affect the pupil dilatation.
Moving deeper
If you look beyond the iris, you can see the front camera. It is here that there are mechanisms due to which intraocular fluid is produced. This substance circulates in the eye, washing its components. In the corner of the chamber there is a drainage system provided for by nature, through which fluid flows from the eye. And in the depths of the ciliary body, you can find accommodation muscle. Thanks to its functioning, the shape of the lens changes.
The choroid is even deeper. The structure of the human eye suggests the presence of the choroid in the back, 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 nutrition of tissues.
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, this is a mesh shell. It is formed by nerve cells. The fabric lines the eye on the inner surface and guarantees high-quality vision, if healthy.
The structure of the retina is such that an image obtained 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 the placement of visual cones. Data obtained by the retina is transmitted to a special nerve, through which it enters the brain, where it is processed quickly.
What's inside?
What is the structure of the human eye, if you look under all three shells? Here you can find two cameras:
Both of them are filled with a special fluid. In addition, there are:
The first in shape resembles a lens convex on both sides. He is able to refract the light flux and transmit it. Thanks to the lens, it becomes possible to focus the image on the reticular nerve tissue. But the vitreous is most like a jelly. Its main task is to prevent the contact of the fundus and the lens.
Fibrous and conjunctival membranes
Studying the location of the structure of the eye, begin with the conjunctiva. It is a transparent tissue outside the eye. It is she who covers the eyelids from the inside. Thanks to the conjunctiva, eyeballs can correctly glide without damage.
Speaking about what are the functions of the structures of the eye, we can not lose sight of the fibrous membrane. Partially, it is created from sclera and has a high density, which guarantees protection of fragile internal contents. This fabric is supportive, but the front is transparent and similar to the glass on the watch. This segment of the fibrous membrane is commonly called the cornea.
The transparent part of the membrane is rich in nerve cells, which guarantees the conductivity of information. In the place where the sclera passes into the cornea, a limb is secreted. Under this term, it is customary to understand the concentration zone 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 is also there. Parsing the location of the shells and structures of the eye, a little further inland you can see the lens. So that he 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 rear cameras are full of colorless moisture. This fluid nourishes the lens, and supplies the necessary nutrients 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 ensured by the presence of refractive structures of the eye. It is due to the complex optics of the visual system that one can perceive data from the environment. The perception of the space around him will be correct if all organs and tissues function normally in a person:
- auxiliary structures of the eye;
- light guide;
- perceiving.
With proper operation, you can have no doubt in the clarity of vision.
Key elements of the optical system:
Note that the refractive 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;
- do not have turbidity.
Only when the rays of light pass through this system, they appear on the retina, where the formation of the image of the surrounding space. Remember that it manifests itself:
In this case, nerve impulses are formed, which enter the nerve and are transmitted to the brain through it. Neurons analyze the information received, so that a person gets a detailed idea of what is surrounding him.
The cornea is a complex element of the ocular system
Different elements belong to the photosensitive structures of the eye, and the cornea is not the least in importance. Five types of fabrics form it:
- epithelium in front;
- Reichert record;
- stroma;
- Descemet's tissue;
- endothelium.
Despite the five components, the thickness of the cornea is only about a millimeter. Please note: although the light-refracting structures of the eye are relatively 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 one millimeter wider in width. The specific 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 to create the cornea is the exclusion of blood vessels. But there are a lot of nerve endings. Several tissues belong to the light-refracting structures of the eye, but it is this organ that has a high refractive power, and it is one of the main ones.
Ciliary body
The photosensitive 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 like a circular roller. Scientists conditionally divide it into two elements:
- vascular, that is, formed by vessels;
- muscle created by the ciliary muscle.
The first component combines about 70 thin processes capable of producing a fluid that provides nutrition and cleansing of the eye structure. Zinn bundles come from here, thanks to which the lens is firmly fixed in its place.
The retina as one of the key elements of the visual system
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:
- Pigmented (it is also external). This element is capable of absorbing light, due to which the scattering phenomenon inside the eye is significantly reduced.
- Processes of cells. Scientists call them flasks and sticks. Rhodopsin and iodopsin are formed in the processes.
- Ocular fundus. This is an active element of the visual system. When examining the eye, it is the ophthalmologist who sees him.
- The vascular layer.
- The nerve disk, indicating the point where the nerve leaves the eye.
- A yellow spot, by which it is customary to understand that part of the tissue where the density of cones is greatest, providing the possibility of color vision of the surrounding space.
What kind of liquid?
More than once, intraocular fluid, which fills the chambers, which is mandatory for the normal functioning of the eye, has been mentioned. Visually and in 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 reservoir. If you examine the eye socket visually, it becomes clear that it is similar to a pyramid with four faces, but as if truncated. The top of the pyramid looks into the skull. The angle of inclination is 45 degrees. In depth, the human eye socket is from 4 to 5 cm.
Please note: the eye socket is really bigger than the eyeball. It is necessary that the fat body, as well as the nerve and muscles, the vascular system, which ensures the correct functioning of the eye, also fit here.
The eyelids are also a component of the structure of the eye.
In a normal healthy human body, each eye has been protected for two centuries:
They help protect the fragile system from falling objects from the outside. The closure of the eyelids occurs unconsciously, the reaction is instantaneous not only in case of serious danger, but even with a wind blow. The eyelids protect the eye when touched.
Blinking movements help cleanse the cornea of dust components. Thanks to them, tear fluid spreads evenly . Also eyelids are equipped with eyelashes growing on the edges. Nowadays, they have become an important element in the concept of human beauty, but nature is primarily conceived to protect the visual system. Thanks to the cilia, the eye is protected from dust and small debris that could damage thin tissues.
The human eyelids are a fairly thin layer of skin that forms folds. Under the epithelium is the muscle layer:
- circular, providing closure;
- lifting 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 performance that has developed over many centuries: "Severe men do not cry," "Cry is shameful!" Is tears true - this is only an indicator of a person’s mental weakness? Nature, creating the lacrimal apparatus, strove to provide protection and correct functioning of the visual system, therefore, in fact, even men can afford to cry, thereby purifying and protecting their eyes.
Tears are such transparent drops of a specific fluid, which are characterized by weak alkalinity. The composition of the tear is very complex, but the key component is pure water. Normal excretion per day is about a milliliter. Tears protect the eyes and help nourish the tissue, and also see better.
The lacrimal apparatus includes:
- gland that produces tears;
- points of tears;
- channels
- bag;
- duct.
The gland is located in the orbit, in the upper part of its wall, on the outside. It is here that tears form, which then fall into the channels intended for this, and from there onto the ocular surface. Excess moisture moves down, where the conjunctival arch is provided for this.
There are two lacrimal openings: above and below. Both of them are in the inner corner, on the edges of the eyelids. Through them, teardrops pass through the channels into a sac close to the wing of the nose, then directly into the nose.
How much muscle in the eye system?
If we study the muscle apparatus, it becomes clear that six muscles are functioning in the human eye. They are divided into the following groups:
The first are divided into:
Straight lines are the remaining four that are known to science under the names:
In addition, the ocular system includes the aforementioned mechanisms for lifting the upper eyelid and squeezing.
Diseases associated with impaired eye structure
It turns out that people suffer from eye diseases at different ages. Eye problems haunt people regardless of their social status, affluence, living conditions, or nationality. However, in some cases, it may be a predisposition associated with genetics, ecology or other factors. Usually eye disorders are provoked by:
- incorrect location of a particular structural element;
- defective parts of the eye.
There are 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;
- myodesopsy.
Most often, myopia and farsightedness have been found recently. In the first case, the eyeball is characterized by a length exceeding 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.
Farsightedness is characterized by the opposite picture. The reason for the violation is that the lens becomes inelastic or the eyeball is reduced in length. Accommodation is weakening, the rays are focused behind the retina, and a person cannot clearly distinguish those objects that are nearby. In this case, prescribe glasses with positive diopters.
Please note: glasses should be prescribed only by an ophthalmologist, it is unacceptable to prescribe yourself lenses or glasses yourself. When selecting, the eye is measured, the distance between the pupils is calculated and the fundus is thoroughly checked, as well as the scale of the violations is revealed. When analyzing all the data obtained, the doctor recommends choosing one or another glass, and may also advise you to have an operation or otherwise correct your vision.
But astigmatism is much less common. With this violation, the brain can not get the correct information about the surrounding space due to a defect of the lens, cornea, which leads to the fact that the ocular membrane loses the shape of a sphere.