Human body of sight. Anatomy and physiology of the organ of vision

Our body interacts with the environment with the help of the senses, or analyzers. With their help, man is not only able to "sense" the external world, on the basis of these sensations he has special forms of reflection - self-consciousness, creativity, the ability to foresee events, etc.

What is the analyzer?

According to IP Pavlov, each analyzer (and even the organ of vision) is nothing but a complex "mechanism". It is able not only to perceive the signals of the environment and convert their energy into momentum, but also to produce higher analysis and synthesis.

The organ of vision, like any other analyzer, consists of 3 integral parts:

- the peripheral part, which is responsible for the perception of the energy of external stimulation and its processing into a nerve impulse;

- conductive paths, through which the nerve impulse passes directly to the nerve center;

- the cortical end of the analyzer (or the sensory center) located directly in the brain.

All nerve impulses from the analyzers come directly to the central nervous system, where all information is processed. As a result of all these actions perception also arises - the ability to hear, see, touch, etc.

As a sense organ, vision is especially important, since without a vivid picture life becomes boring and uninteresting. It provides 90% of information from the environment.

The eye is the organ of vision, which has not yet been studied to the end, but there is still a representation about it in anatomy. And that is what will be discussed in this article.

Anatomy and physiology of the organ of vision

Let's look at everything in order.

The eye is the eyeball with the optic nerve and some auxiliary organs. The eyeball has a globular shape, usually large in size (its size in an adult is ~ 7.5 cubic cm). It has two poles: the rear and the front. It consists of a nucleus, which is formed by three membranes: fibrous membrane, vascular and retina (or internal membrane). This is the anatomy of the organ of vision. Now about each part in more detail.

Fibrous membrane of the eye

The outer shell of the nucleus consists of a sclera, a posterior part, a dense connective tissue membrane and a cornea, a transparent convex part of the eye devoid of blood vessels. The cornea is about 1 mm in thickness and about 12 mm in diameter.

Below is a diagram showing the organ of vision in a section. There you can see in detail where this or that part of the eyeball is located.

Vascular membrane

The second name for this core shell is the choroid. It is located directly under the sclera, is saturated with blood vessels and consists of 3 parts: the vascular membrane itself, as well as the iris and ciliary body of the eye.

Vascular membrane is a dense network of arteries and veins, intertwined with each other. Between them is a fibrous, loose connective tissue that is rich in large pigment cells.

From the front, the vascular membrane smoothly passes into a thickened ciliated body of annular shape. Its direct purpose is the accommodation of the eye. The ciliary body supports, fixes and stretches the lens. It consists of two parts: the inner (ciliary crown) and the outer (ciliary circle).

From the ciliary cup to the lens, about 70 ciliated processes extend about 2 mm long. To the processes attach the fibers of the zinn ligament (ciliary band), reaching the lens of the eye.

A ciliary band almost entirely consists of the ciliary muscle. When it contracts, the lens is straightened and rounded, after which its bulge (and with it the refractive force) increases, and accommodation takes place.

Due to the fact that ciliary muscle cells atrophy at an old age and in their place connective tissue cells appear, accommodation deteriorates and farsightedness develops. In this case, the organ of vision does not do well with its functions, when a person tries to look at something nearby.

Iris

Iris is a circular disk with an opening in the center - a pupil. It is between the lens and the cornea.

In the vascular layer of the iris, two muscles pass. The first forms the dilator (sphincter) of the pupil; The second, on the contrary, dilates the pupil.

It is the amount of melanin in the iris that determines the color of the eye. Photos of possible options are attached below.

The smaller the pigment in the iris, the lighter the color of the eyes. The body of vision performs its functions in the same way, irrespective of the color of the iris.

Gray-green eye color also means only a small amount of melanin.

The dark color of the eye, the photo of which is higher, indicates that the level of melanin in the iris is high.

Internal (photosensitive) shell

The retina is completely attached to the choroid. It is formed by two sheets: external (pigmented) and internal (photosensitive).

In a ten-layer photosensitive shell, three-neuron radially oriented chains are distinguished, represented by the photoreceptor outer layer, associative middle and ganglionic inner layers.

Outside the vascular membrane is attached a layer of epithelial pigment cells that are closely in contact with the layer of cones and rods. Both those and others are nothing but peripheral processes (or axons) of photoreceptor cells (neuron I).

Sticks consist of the inner and outer segments. The latter is formed by double membrane discs, which are the folds of the plasma membrane. The cones differ in size (they are larger) and in the nature of the disks.

In the retina, the eyes distinguish three types of cones and only one kind of rods. The number of rods can reach 70 million, and even more, while cones - only 5-7 million.

As already mentioned, there are three types of cones. Each of them perceives a different color: blue, red or yellow.

Wands are needed to perceive information about the shape of the object and the illumination of the room.

A thin process emerges from each of the photoreceptor cells, which forms a synapse (the place where two neurons contact) with another process of bipolar neurons (neuron II). The latter transmit excitation to larger ganglion cells (neuron III). The axons (processes) of these cells form the optic nerve.

Lenticular

This is a biconvex crystal-clear lens with a diameter of 7-10 mm. Has no nerves, no vessels. Under the influence of the ciliary muscle, the lens can change its shape. It is these changes in the shape of the lens that are called the accommodation of the eye. When set to a distant vision, the lens is flattened, and with near vision - increases.

Together with the vitreous body, the lens forms the light-refracting environment of the eye.

Vitreous body

They filled all the free space between the retina and the lens. Has a jelly-like transparent structure.

The structure of the organ of vision is similar to the principle of the device of the camera. The pupil performs the role of the diaphragm, tapering or widening depending on the illumination. As an objective, the vitreous body and the lens. The light rays fall on the retina, but the image is then turned upside down.

Thanks to the light-refractive media (thereby the lens and the vitreous body), the light beam hits the yellow spot on the retina, which is the best zone of vision. The cones and rods light waves are reached only after the entire thickness of the retina has passed.

Motor vehicle

The motor apparatus of the eye is made up of striated 4 straight muscles (lower, upper, lateral and medial) and 2 oblique (lower and upper). The straight muscles are responsible for turning the eyeball in the appropriate direction, and the oblique muscles are responsible for the turns around the sagittal axis. The movements of both eyeballs are synchronous only due to the muscles.

Eyelids

Skin folds, whose purpose is to limit the eye gap and close it when closing, provide protection to the eyeball in front. In each century there are about 75 eyelashes, the purpose of which is to protect the eyeball from getting foreign object.

Approximately once in 5-10 seconds a person blinks.

The lacrimal apparatus

It consists of lacrimal glands and a system of lacrimal passages. Tears detoxify microorganisms and are able to moisten the conjunctiva. Without the tears of the conjunctiva, the eyes and the cornea would simply dry out, and the person would be blind.

Tear glands daily produce about one hundred milliliters of tears. An interesting fact: women cry more often than men, because the secretion of tear fluid is promoted by the hormone prolactin (which the girls have much more).

Basically, the tear consists of water containing about 0.5% albumin, 1.5% sodium chloride, a little mucus and lysozyme, which has a bactericidal effect. Has a slightly alkaline reaction.

The structure of the human eye: a diagram

Let's take a closer look at the anatomy of the organ of vision with the help of drawings.

The figure above shows schematically the parts of the organ of vision in a horizontal section. Here:

1 - tendon of the middle rectus muscle;

2 - the back chamber;

3 - cornea of the eye;

4 - the pupil;

5 - crystalline lens;

6 - anterior chamber;

7 - iris of the eye;

8 - conjunctiva;

9 - tendon of the lateral muscle;

10 - vitreous body;

11 - sclera;

12 - choroid;

13 - the retina;

14 - yellow spot;

15 - optic nerve;

16 - blood vessels of the retina.

This figure shows the schematic structure of the retina. The arrow shows the direction of the light beam. The figures are:

1 - sclera;

2 - choroid;

3 - retinal pigment cells;

4 - sticks;

5 - cones;

6 - horizontal cells;

7 - bipolar cells;

8 - amacrine cells;

9 - ganglion cells;

10 - optic nerve fibers.

The figure shows the scheme of the optical axis of the eye:

1 is an object;

2 - cornea of the eye;

3 - the pupil;

4 - iris;

5 - crystalline lens;

6 - the central point;

7 is an image.

What functions does the body perform?

As already mentioned, human vision transmits almost 90% of information about the world around us. Without it, the world would be the same type and uninteresting.

The organ of vision is quite complex and not fully understood by the analyzer. Even in our time, scientists sometimes have questions about the structure and purpose of this body.

The main functions of the organ of vision are the perception of light, the forms of the surrounding world, the position of objects in space, and so on.

Light can cause complex changes in the retina of the eye and, thus, is an adequate stimulus for the organs of vision. It is believed that the first perceives the irritation of rhodopsin.

The most qualitative visual perception will be provided that the image of the subject falls on the area of the retina, preferably on its central fossa. The farther from the center the projection of the image of the object, the less distinctly. This is the physiology of the organ of vision.

Diseases of the organ of vision

Let's look at some of the most common diseases of the eye.

1. Farsightedness. The second name for this disease is hypermetropia. A person with this ailment does not see objects that are close. Usually difficult to read, work with small objects. Usually it develops in people of age, but it can also appear in young people. Completely cure hyperopia is possible only with the help of an intervention.
2. Myopia (it is also called myopia). The disease is characterized by the inability to clearly see objects that are far enough away.
3. Glaucoma - increased intraocular pressure. Occurs because of a violation of the circulation of fluid in the eye. It is treated medically, but in some cases surgery may be required.
4. Cataract is nothing but a violation of the transparency of the lens of the eye. Help to get rid of this disease can only an ophthalmologist. Surgery is required, in which the vision of a person can be restored.
5. Inflammatory diseases. These include conjunctivitis, keratitis, blepharitis, and others. Each of them is dangerous in its own way and has different methods of treatment: some can be cured with medicines, and some can only be cured by surgery.

Prevention of diseases

First of all, you need to remember that your eyes also need to rest, and excessive loads will not lead to anything good.

Use only high-quality lighting with a lamp power of 60 to 100 watts.

Often spend gymnastics for the eyes and at least once a year undergo an examination with an ophthalmologist.

Remember that eye diseases are a serious threat to the quality of your life.