What does the human eye consist of? Lacrimal apparatus of the eye
The human eye is a very complex optical system, sensitive to external stimuli. The eye is unique paired organ through which we see. It is very vulnerable to damage and disease. Each person's eye has its own individual characteristics, unlike others.
Free movements of the eyeball allow us to see the world with both eyes. The lacrimal glands constantly moisturize the eyeball. They also contribute to the formation of a thin protective film. It is believed that the eye is as complex an organ as human brain. The organs of vision have not been fully studied. The shape is spherical. The diameter is 24 mm, and the average length is about 24 mm.
Functions of the organs of vision
As we have already said, the eye is a complex optical device, the main task of which is to transmit an image to the optic nerve.
Its main functions are:
- an optical system that projects the image;
- a system that perceives and encodes information;
- life supporting system.
Structure of the human eye
In itself, such a small organ has a rather impressive and intricate structure. All components are interconnected. The organ consists of the following parts:
- The cornea is a convex transparent part of the eyeball without blood vessels, which has a high refractive power. It borders on the sclera and occupies approximately 1/6 of the outer shell of the eye.
- The anterior chamber is the space between the cornea and the iris, filled with intraocular fluid.
- The iris is a thin transparent diaphragm that resembles a circle with a hole inside. It consists of muscles, due to the contraction and relaxation of which the size of the pupil changes. The iris is part of the choroid of the human eye. The color of the organ of vision also depends on it. Its function is to regulate light flow.
- The pupil is a hole located in the iris. Light rays enter the eye through it.
- The lens is a part of the organ of vision, similar to a lens, located inside the eyeball. This is the so-called biological lens. The lens has a transparent color and is very elastic. Capable of changing shape. It is held in place by the ciliary girdle and enters optical system.
- Vitreous body- This is a transparent substance that is located in the posterior part of the eye and is part of the optical system. Its function is to maintain the shape of the eyeball. The vitreous body also takes part in intraocular metabolism.
- The retina is the inner layer of the eye and consists of photoreceptors and nerve cells. It has a diametrical size and is adjacent to the choroid.
- The sclera is an opaque outer membrane containing six oculomotor muscles. Largest quantity nerve endings located precisely in the sclera. middle part eyes.
- Choroid - covers posterior section sclera and is responsible for the blood supply to intraocular structures. There are no nerve endings here.
- Optic nerve - helps transmit signals from nerve endings to the human brain.
- The ciliary body is part of the choroid, as well as a complex neuro-endocrine organ that takes part in the production of eye fluid.
- The muscular system is involved in the movement of the eyeball and consists of eight muscles. Thanks to these muscles, the eyeball is able to move in different directions.
- Lacrimal apparatus- consists of the lacrimal glands, which are located in the upper outer wall of the orbit, lacrimal canaliculi, and also in the lacrimal sac. In humans, lacrimation increases due to irritation of the cornea.
The protective apparatus of the human eye consists of the eyelids and the orbit.
The eyelids are movable folds located around the eye. They protect it from damage and also help focus vision. On front layer The upper and lower eyelids contain eyelashes. At the edge of the upper and lower eyelids there are lacrimal puncta, which are the beginning of the lacrimal canaliculi. Thin skin covers the outer surface of the eyelids.
The orbit is a paired cavity that contains the eyeball with its appendages. The orbit is a pyramidal cavity with a base, apex and four walls.
Facts about the human eye
In addition to vision, a person has other senses, but we receive 80% of information through the eyes. These organs have the ability to capture images, thanks to which visual images remain in our memory. At the next meeting with a specific person or object, the organ of vision activates memories, that is, the person visually remembers what he saw. The human eye resembles a camera, but it is many times greater than even the most modern device. Organ human vision able to record information and transmit it to the brain.
Even though a person has two eyes, he can only see what is happening in front of him. For example, a horse's eyes are located on the sides, which allows it to see with peripheral vision and react in time to danger.
The eye can recognize up to 10 million colors. No one on Earth except humans has such an ability. A person blinks for about 12 minutes a day. If he did not do this, his vision would be very poor and his eyeball would also dry out. A person blinks for the first time at six months.
Interestingly, no one can sneeze without closing their eyes for a couple of seconds. This phenomenon is associated with the reaction of nerve endings. The human eye is similar in structure to the eye of a shark. Today in China, operations are being carried out to restore human vision by transporting the cornea of this sea creature.
Diseases and care
Ophthalmologists treat eye diseases. Alas, the eyes are very vulnerable to various kinds ailments. There are many eye diseases that can be either congenital or acquired. The main diseases are:
- conjunctivitis;
- cataract;
- retinopathy;
- color blindness;
- keratitis;
- astigmatism;
- strabismus;
- glaucoma.
In addition, eye damage can occur due to such infectious diseases, like trachoma, syphilis, tuberculosis and some others.
You need to take good care of your eyes, not only to protect them from disease, but also to keep them beautiful and fresh. They are an extremely vulnerable organ that should be treated with special care. If your eyes have been very tense during the day, you should definitely give them a rest. You should also perform simple exercises so that your visual organs rest and relax.
It is recommended to place tampons with herbal infusion on your eyelids at night. In addition, your eyes should be washed regularly with room water, as dust gets into them, which can cause redness. Women are advised to choose cosmetics very carefully, as they can harm the eyes, cause allergies and other diseases.
Among other things, doctors recommend wiping around the eyes with a special lotion every day to prevent the skin from drying out. The most important thing is that the lotion does not contain alcohol. It is enough to spend 10-15 minutes a day on eye care, and you will see how much healthier and more attractive you look.
The eyes are a complex organ in structure, since they contain various working systems that perform many functions aimed at collecting information and transforming it.
The visual system as a whole, including the eyes and all their biological components, includes more than 2 million constituent units, which include the retina, lens, cornea, nerves, capillaries and vessels, iris, macula and optic nerve occupy an important place.
A person must know how to prevent diseases associated with ophthalmology in order to maintain visual acuity throughout his life.
In order to understand what the human eye is, it is best to compare the organ with a camera. Anatomical structure presented by:
- Pupil;
- Cornea (colorless, transparent part of the eye);
- Iris (it determines the visual color of the eyes);
- Lens (responsible for visual acuity);
- Ciliary body;
- Retina.
The following structures of the ocular apparatus also help ensure vision:
- Choroid;
- Optic nerve;
- The blood supply is carried out by nerves and capillaries;
- Motor functions are carried out by the eye muscles;
- Sclera;
- Vitreous body (main defense system).
Accordingly, elements such as the cornea, lens and pupil act as the “lens”. The light falling on them or Sun rays are refracted and then focused on the retina.
The lens is “autofocus”, since its main function is to change the curvature, due to which visual acuity is maintained at normal levels - the eyes are able to clearly see surrounding objects at different distances.
The retina acts as a kind of “photo film”. The image seen remains on it, which is then transmitted in the form of signals using optic nerve to the brain, where processing and analysis occur.
Know common features the structure of the human eye is necessary to understand the principles of operation, methods of prevention and treatment of diseases. It is no secret that the human body and each of its organs is constantly improving, which is why the eyes, in evolutionary terms, managed to achieve a complex structure.
Due to this, structures of different biology are closely interconnected in it - vessels, capillaries and nerves, pigment cells, and also takes part in the structure of the eye Active participation connective tissue. All these elements help coordinated work organ of vision.
Anatomy of the eye: main structures
Eyeball or directly human eye, It has round shape. It is located in a cavity in the skull called the orbit. This is necessary because the eye is a delicate structure that is very easy to damage.
The protective function is performed by the upper and lower eyelids. Visual movement of the eyes is provided by extrinsic muscles called the oculomotor muscles.
The eyes need constant hydration - this function is performed by the lacrimal glands. The film they form additionally protects the eyes. The glands also ensure the drainage of tears.
Another structure related to the structure of the eyes and providing their direct function is the outer shell - the conjunctiva. It is also located on inner surface upper and lower eyelids, is thin and transparent. Function: sliding during eye movement and blinking.
The anatomical structure of the human eye is such that it has another important membrane for the organ of vision - the sclera. It is located on the front surface, almost in the center of the organ of vision (eyeball). The color of this formation is completely transparent, the structure is convex.
The directly transparent part is called the cornea. She is the one who has hypersensitivity to various kinds of stimuli. This happens due to the presence of many nerve endings in the cornea. The lack of pigmentation (transparency) allows light to penetrate inside.
The next eye shell forming this important organ– vascular. Besides providing eyes required quantity blood, this element is also responsible for regulating tone. The structure is located from the inside of the sclera, lining it.
Every person's eyes have a certain color. A structure called the iris is responsible for this sign. Differences in shades are created due to the pigment content in the very first (outer) layer.
This is why eye color is not the same different people. The pupil is the hole in the center of the iris. Through it, light penetrates directly into each eye.
The retina, despite being the thinnest structure, is the most important structure for the quality and acuity of vision. At its core, the retina is nerve tissue, consisting of several layers.
The main optic nerve is formed from this element. That is why visual acuity and the presence of various defects such as farsightedness or myopia are determined by the condition of the retina.
The vitreous body is commonly called the cavity of the eye. It is transparent, soft, almost jelly-like in feel. The main function of the formation is to maintain and fix the retina in the position necessary for its operation.
Optical system of the eye
Eyes are one of the most anatomically complex organs. They are a “window” through which a person sees everything that surrounds him. This function can be performed by an optical system consisting of several complex, interconnected structures. The composition of “eye optics” includes:
- Lens;
Accordingly, they perform visual functions– transmission of light, its refraction, perception. It is important to remember that the degree of transparency depends on the state of all these elements, therefore, for example, if the lens is damaged, a person begins to see the picture unclearly, as if in a haze.
The main element of refraction is the cornea. The light flux hits it first, and only then enters the pupil. It, in turn, is a diaphragm on which light is additionally refracted and focused. As a result, the eye receives an image with high clarity and detail.
Additionally, the lens also performs the function of refraction. After the light flux hits it, the lens processes it, then transmits it further - to the retina. Here the image is “imprinted”.
The liquid and vitreous body present slightly contribute to refraction. However, the state of these structures, their transparency, sufficient quantity, provide big influence on the quality of human vision.
The normal operation of the eye optical system leads to the fact that the light falling on it undergoes refraction and processing. As a result, the image on the retina is reduced in size, but completely identical to the real one.
Also note that it is upside down. A person sees objects correctly, since the finally “imprinted” information is processed in the corresponding parts of the brain. That is why all elements of the eyes, including blood vessels, are closely interconnected. Any minor violation leads to loss of visual acuity and quality.
How the human eye works
Based on the functions of each anatomical structure, we can compare the principle of operation of the eye to a camera. Light or an image first passes through the pupil, then penetrates the lens, and from it to the retina, where it is focused and processed.
The constituent elements - rods and cones - contribute to sensitivity to penetrating light. Cones, in turn, allow the eyes to perform the function of distinguishing colors and shades.
Violation of their work leads to color blindness. After the refraction of the light flux, the retina translates the information imprinted on it into nerve impulses. They then enter the brain, which processes it and outputs the final image that a person sees.
Prevention of eye diseases
Eye health must be maintained at all times high level. That is why the issue of prevention is extremely important for any person. Testing your visual acuity in a doctor's office isn't your only eye care concern.
It is important to monitor the health of the circulatory system, as it ensures the functioning of all systems. Many of the irregularities identified are the result of a lack of blood or irregularities in the feeding process.
Nerves are elements that also have important. Their damage leads to impaired quality of vision, for example, the inability to distinguish the details of an object or small elements. That is why you should not overstrain your eyes.
At long work It is important to give them a rest every 15-30 minutes. Special gymnastics Recommended for those involved in work that involves long-term examination of small objects.
In the process of prevention, one should Special attention pay attention to the illumination of the work space. Nourishing the body with vitamins and minerals, eating fruits and vegetables helps prevent many eye diseases.
Inflammations should not be allowed to form, as this can cause suppuration, therefore proper hygiene the eye is a good way of preventive treatment.
Thus, the eyes are a complex object that allows us to see the world around us. It is necessary to take care and protect them from diseases, then their vision will retain its sharpness for a long period.
The structure of the eye is shown in great detail and clearly in the following video.
The sclera is the dense, opaque outer layer of the eye, which consists of connective tissue and ensures the constant shape of the eye.
Choroid
The choroid of the eye consists of the iris, ciliary body and choroid. It has two blood supply systems: the system of posterior long and anterior ciliary arteries (for the iris and ciliary body), the system of posterior short ciliary arteries (for the choroid). Reacts to any exo- and endogenous factors
Choroid
The choroid is the actual choroid of the eye. The main function of the choroid is to nourish the retina, restore constantly decaying visual substances
Macula (macula)
The macula (macula) is the central area of the retina, onto which the light beam is focused, has the highest concentration of cones, which ensures high central visual acuity
Optic disc
The optic disc is the area of the fundus where retinal ganglion cell fibers converge to form the optic nerve. Is an oval pale pink with clear boundaries with a diameter of 1.5-1.8 mm. They come out of it central artery and retinal vein
Retina
The retina is the innermost layer of the eyeball, which is a thin transparent film of nerve tissue.
The retina consists of neurons: photoreceptor neuroepithelium (rods and cones); bipolar cells; ganglion cells. Lies on the choroid, from which it is separated by the pigment epithelium (it forms and contains visual substances) and Bruch’s membrane (promotes selective penetration of nutrients and removal of waste from the retina)
Optic nerve
The optic nerve is white matter brain Has shells that are a continuation meninges. It is part of the visual pathway.
Proprietary substance of the cornea, or stroma
Makes up most of the entire thickness of the cornea. It consists of thin, regularly alternating connective tissue plates, the processes of which contain many very fine fibrils. The role of a cementing substance between the fibrils is performed by an adhesive mucoid, which contains the sulfur salt of sulfohyaluronic acid, which ensures the transparency of the main substance of the cornea
Posterior corneal epithelium, or endothelium
The posterior corneal epithelium, or endothelium, is a layer of flat cells tightly packed together. Responsible for metabolic processes between the cornea and the moisture of the anterior chamber, plays important role in ensuring corneal transparency. When it is damaged, swelling appears
Posterior limiting plate of the cornea, or Descemet's membrane
A characteristic feature of the posterior limiting plate is resistance to chemical reagents; it is important as protective barrier from bacterial invasion and capillary ingrowth. Descemet's membrane can resist lytic attack purulent exudate for corneal ulcers, regenerates well and quickly recovers in case of destruction, in case of damage it gapes, its edges curl
Anterior limiting plate, or Bowman's membrane of the cornea
Shell thickness - 6-9 mm. Is a modified hyalinized part of the stroma, has the same chemical composition, as the cornea's own substance. Towards the periphery of the cornea, the anterior border plate becomes thinner and ends 1 mm from the edge of the cornea. Does not regenerate after damage
Iris
The iris is the anterior part of the choroid. In the center is the pupil - a hole that acts as a diaphragm (it regulates the amount of light entering the eye). Its expansion and contraction is ensured by the work of the muscles located in the iris. Each person's iris has its own unique "pattern"
Anterior corneal epithelium
The anterior epithelium of the cornea is a continuation of the epithelium of the conjunctiva. Has high regenerative ability. Clinical observations show that corneal defects are restored with amazing speed due to the proliferation of cells in the superficial layer. Even with almost complete rejection, the epithelium recovers within 1-3 days
Sclera
The sclera consists of its own substance, which forms its main mass, a suprascleral plate - episclera, an internal layer with a slightly brown tint - the brown plate
The sclera plays the role of a “framework” for the internal and external elements of the eyeball. The extraocular muscles are attached to it. The spherical shape of the eyeball is created, on the one hand, by the elastic properties of the sclera, and on the other, by pressure internal environments eyes to sclera
Middle layer of the eye
Iris (anterior part vascular tract).
The ciliary body (an intermediate link between the iris and the choroid proper).
Choroid (actually the choroid of the eye).
The vascular tract is the main collector of nutrition for the eye. It plays a dominant role in intraocular metabolic processes. At the same time, each section of the vascular tract anatomically and physiologically performs special functions inherent to it.
Ciliary or ciliary body
The uveal, or mesodermal, component is a continuation of the choroid.
1. Suprachoroid. When contracted, the meridional fibers pull the choroid anteriorly (its other name is the Brücke muscle).
2. Muscle layer. The combined contraction of all bundles of the ciliary (accommodative) muscle provides the accommodative function ciliary body.
The radial portion of the ciliary muscle extends from the scleral spur to the ciliary processes and the pars plana of the ciliary body. This part is called the Ivanov muscle
Circular muscle fibers are defined as Müller's muscle.
3. Vascular layer with ciliary processes. Consists of loose connective tissue containing a large number of vessels, elastic fibers and pigment cells. The processes of the ciliary body, which produce intraocular fluid, are especially rich in vessels.
4. Basal plate - Bruch's membrane. Structureless basal plate. Adjacent to it is a layer of pigmented epithelial cells followed by a layer of non-pigmented columnar epithelium
Retinal, or neuroectodermal, is a continuation of the retina and its two epithelial layers. It consists of two layers of epithelium: pigmented and non-pigmented.
Choroid of the eye (choroid)
The choroid of the eye is the energy base that ensures the restoration of the continuously decaying visual purple necessary for vision. Throughout the optical zone, the retina and choroid interact in the physiology of the act of vision.
Iris
The iris of the eye does not have direct contact with the outer shell.
Between it and the cornea there remains free space - the anterior chamber of the eye, filled with liquid contents - chamber, or aqueous, humor.
The iris has the appearance of a thin, almost round plate; horizontal diameter - 12.5 mm, vertical - 12 mm.
In the center of the iris there is a round hole - the pupil, which serves to regulate the amount of light rays penetrating into the eye. The size of the pupil changes depending on the strength of the light flux. average value- 3 mm (largest - 8 mm, smallest - 1 mm).
The anterior surface of the iris has radial striations, which gives it a lacy pattern and relief. Slit-like depressions in the stroma of the iris are called crypts, or lacunae.
Parallel to the pupillary edge, retreating 1.5 mm, there is a serrated ridge, or mesentery. They divide the iris into two zones: the inner - pupillary, and the outer - ciliary.
In the outer part of the ciliary zone, concentric contraction grooves are determined - a consequence of the contraction and straightening of the iris during its movement.
The iris of the eye has two muscles: the sphincter, which constricts the pupil, and the dilator, which causes its dilation. As a result of the interaction between the sphincter and the dilator, the iris acts as a diaphragm that regulates the flow of light rays. The sphincter receives innervation from the oculomotor nerve, and the dilator from the sympathetic nerve.
Anterior iris: The anterior mesodermal layer includes the outer limiting layer and the stroma of the iris.
Posterior, or retinal, part of the iris: the posterior ectodermal layer is represented by the dilator with its internal boundary and pigment layers. The latter forms a pigment fringe or border at the pupillary edge. The sphincter also belongs to the ectodermal layer, which moved into the stroma of the iris during its embryonic development
Lacrimal gland
The lacrimal gland is located under the upper outer edge of the orbit in the fossa of the same name. It is divided into a larger - orbital, and a smaller - palpebral part.
Orbital part of the gland
Hidden by the overhanging supraorbital margin frontal bone and is immersed in the lacrimal fossa, inaccessible for palpation and palpable only when pathological changes- inflammation or tumors
Palpebral part of the gland
Can be seen when turned out upper eyelid and a sharp turn of the eye downward and inward. In this case, it protrudes above the eyeball from the outside under the conjunctiva of the upper fornix in the form of a slightly tuberous yellowish formation
Cameras of the eye
The chambers of the eye are filled with aqueous humor - a transparent, colorless liquid with a density of 1.005-1.007 and a refractive index of 1.33. The amount of moisture in a person does not exceed 0.2-10.5 ml. The aqueous humor produced by the ciliary body contains salts, traces of protein, and ascorbic acid.
Front camera. A space in which the anterior wall is formed by the cornea, the posterior wall by the iris, and in the area of the pupil by central part anterior capsule of the lens. The place where the cornea passes into the sclera, and the iris into the ciliary body, is called the anterior chamber angle. At the apex of the anterior chamber angle there is a supporting frame of the chamber angle - the corneoscleral trabecula. Trabecula, in turn, is inner wall venous sinus of the sclera, or Schlemm's canal. The skeleton of the angle and the venous sinus of the sclera are the main route for the outflow of intraocular fluid.
Rear camera. Located behind the iris, which is its front wall. Outer wall serves as the ciliary body, the posterior surface is the anterior surface of the vitreous body. The entire space of the posterior chamber is permeated with fibrils of the ciliary girdle, which support the lens in a suspended state and connect it to the ciliary body
Posterior chamber of the eye
The posterior chamber of the eye is the space inside the eyeball, located behind the iris between the outer part of the iris and outer surface ligament of cinnamon.
Connective, or mucous membrane of the eye (conjunctiva)
The conjunctiva is a thin membrane that lines the back of the eyelids and the eyeball up to the cornea.
Conjunctival sac. When the palpebral fissure is closed, the connective membrane forms a closed cavity - a narrow slit-like space between the eyelids and the eye.
Conjunctiva of the eyelids. The part of the conjunctiva that covers the back of the eyelids.
Conjunctiva of the eyeball or sclera. Part of the conjunctiva covering the anterior segment of the eyeball.
Conjunctiva transitional folds, or fornix. The part where the conjunctiva of the eyelids, forming the vaults, passes onto the eyeball.
Rudiments of the third century. A vertical semilunar fold covering the eyeball at the inner corner of the palpebral fissure and the lacrimal caruncle - a formation similar in structure to the skin
Physiological functions of the conjunctiva
Protective
Sensitive innervation provides the sensation of a foreign body, while the secretion of tears increases, blinking movements become more frequent, as a result of which the foreign body is mechanically removed from the conjunctival cavity
The secretion of the conjunctival glands, constantly wetting the surface of the eyeball, acts as a lubricant that reduces friction during its movements.
Trophic
The secretion of the conjunctival glands performs the trophic function of the cornea
Barrier
It is carried out due to the abundance of lymphoid elements in the submucosa of the adenoid tissue.
Lens
The lens is isolated from the rest of the eye membranes by a capsule and does not contain nerves or blood vessels. In this regard, inflammatory processes cannot occur in the lens.
In an adult, the lens is a transparent, slightly yellowish, strongly refracting body, shaped like a biconvex lens. Its refractive power is on average 18.0 diopters. The lens is located between the iris and the vitreous body, in the recess of the anterior surface of the latter. It is held in this position by the fibers of the ciliary girdle, which at their other end are attached to the inner surface of the ciliary body. The consistency of the lens in young years is soft.
With age, the density of the neutral part of the lens increases, so it is customary to distinguish the lens cortex and the lens nucleus. The lens has an equator and two poles - anterior and posterior. Divided into anterior and posterior surfaces. The line connecting the anterior and posterior poles is called the axis of the lens. The lens consists of a capsule, capsule epithelium and fibers. The lens capsule is divided into anterior and posterior. The formation of fibers occurs throughout life, which leads to an increase in the volume of the lens.
Anterior chamber of the eye
The anterior chamber is the space formed in front by the cornea, behind by the iris, and in the area of the pupil by the lens. The anterior chamber angle is the peripheral part of the anterior chamber (the angle formed by the cornea and iris). Provides outflow of intraocular fluid
Emmetropia and ametropia
IN normal eye The cornea and lens focus the image of a distant object onto the retina. Focusing is carried out mainly by the cornea, which cannot change its shape. The intraocular muscles may slightly change the shape of the lens. This allows a person to focus their eyes at close range when reading. If the far point of the eye is infinitely distant, then such an eye is called normal or emmetropic. This means that the optical apparatus of the eye (cornea and lens) has a focal length equal to length axis of the eye, and the focus in this case falls exactly on the retina. With emmetropia, images from distant objects are focused in fovea retina. The discrepancy between the far point and the infinitely distant point is called ametropia of the eye. Ametropia of the eye is expressed in diopters - as the reciprocal of the distance from the first surface of the eye to the far point, expressed in meters.
Vitreous body
The vitreous fills the cavity of the eyeball, with the exception of the anterior and posterior chambers of the eye, and thus helps maintain its turgor, conducts light, and participates in intraocular metabolism.
Zinn's ligaments
The ligaments of Zinn are thin fibers running from the ciliary body to the lens, which provide correct position lens in the eye. Participate in accommodation
Cornea
The cornea is the transparent part of the outer layer of the eyeball. It is the main refractive medium of the eye. The outside is covered with a tear film, which provides hydration and protection from exposure unfavorable factors external environment
Ciliary body
The ciliary body is part of the choroid of the eye.
Purpose. Contains muscles that provide accommodation. Its processes produce intraocular fluid, which ensures constancy intraocular pressure and delivers nutrients to the lens, cornea, vitreous body
EYE (lat. oculus) - an organ of vision that perceives light stimulation; is a part visual analyzer(it also includes the optic nerve, which connects G. with the visual centers in the cerebral cortex). Eyeball - paired formation almost correct spherical approximately 24 mm in diameter, located in the eye socket, or orbit. Its mobility is ensured by the activity of the extraocular muscles. In front, G. is protected by centuries. The tear fluid that washes the eyes is secreted by paired lacrimal glands located at the upper outer edges of the orbits.
The wall of the eyeball consists of three membranes: a very dense outer (fibrous) membrane - the sclera, which passes in the anterior part into a transparent cornea, which is optically comparable to a strong convex lens; middle (vascular) and inner (retina, or retina) membranes. Inside the eyeball there is a lens (a transparent, light-refracting elastic formation shaped like a biconvex lens) and a vitreous body (a transparent gelatinous mass).
The chambers of the eyeball are filled with transparent intraocular fluid - aqueous humor. In the anterior part of the choroid is the iris, through a round hole in which (the pupil) light rays penetrate into the eyeball and reach the retina. Depending on the intensity of the light flux, the pupil is able to change its size: in bright light it is narrower, in weak light and in the dark it is wider. The size of the pupil changes as a result of the interaction of smooth muscles - the sphincter (constricts the pupil) and the dilator (dilates the pupil); the size of the pupils may be different (see Anisocoria). The iris contains pigment, the individual amount of which determines the so-called. eye color. Light stimuli are perceived by the posterior 2/3 retina - its optical part, which has a very complex structure. The outer layers of the retina are composed of cells called cones and rods for their shape, which are photoreceptors, providing color and light perception, respectively. The highest visual acuity is achieved in the area macular spot retina, medially from which the optic disc is located. These fundus formations are visible during ophthalmoscopic examination and assessment of their condition is important in recognizing many diseases.
The refractive power of a lens is measured in diopters (the power of a lens with focal length 1m). For clear vision, the focus of the rays entering the lens from objects under consideration, located at different distances from the observer, must coincide with the retina. This is ensured by a change in the refractive power of the eye - accommodation of the eye.
Malformations of the eyeball or its parts may be hereditary or result from exposure of the fetus to various harmful factors. The most severe malformation is the absence of a gland (anophthalmos); more often, a sharp decrease in the size of the gland is observed - microphthalmos. Pigmentation disorders are caused by different colors of the irises of the right and left G., which usually does not affect vision.
Severe consequences (up to the formation of a cataract, the formation of cataracts) are accompanied various damages G. - his burns, wounds, penetration foreign bodies and others, which, along with increased intraocular pressure (glaucoma), often lead to significant visual impairment and blindness. See also Astigmatism, Myopia, Farsightedness, Keratitis, Conjunctivitis.
Undoubtedly, each of the senses is important and necessary for a person to fully perceive the world around him.
Vision allows people to see the world as it is - bright, diverse, unique.
Organ - vision
IN human organ- vision - can be distinguished the following components:
- The peripheral zone is responsible for the correct perception of the initial data. In turn, it is divided into:
- eyeball;
- protection system;
- adnexal system;
- motor system.
- The area responsible for conducting nerve signals.
- Subcortical centers.
- Cortical visual centers.
Anatomy of the human eye structure
The eyeball looks like a ball. Its location is concentrated in the orbit, which has high strength thanks to bone tissue. Eyeball from bone formation separates fibrous membrane. The motor activity of the eye is carried out thanks to the muscles.
Outer shell of the eye presented connective tissue. The anterior zone is called the cornea and has a transparent structure. The posterior zone is the sclera, better known as the protein. Thanks to the outer shell, the shape of the eye is round.
Cornea. A small part of the outer layer. The shape resembles an ellipse, the dimensions of which are as follows: horizontal - 12 mm, vertical - 11 mm. The thickness of this part of the eye does not exceed one millimeter. Distinctive feature corneas – complete absence blood vessels. The cells of the cornea form a clear order, which is what makes it possible to see the picture undistorted and clear. The cornea is a convex-concave lens with a refractive power of approximately forty diopters. The sensitivity of this area of the fibrous layer is very significant. This is explained by the fact that the zone is the location of nerve endings.
Sclera (protein). It is opaque and durable. The composition includes fibers that have elastic structure. The muscles of the eye are attached to the protein.
Middle layer of the eye. Presented blood vessels and is divided by ophthalmologists into the following zones:
- iris;
- ciliary body or ciliary body;
- choroid.
Iris. A circle in the center of which, in a special hole, the pupil is located. The muscles located inside the iris allow the pupil to change in diameter. This happens when they contract and relax. It is important to note that the designated zone determines the shade of human eyes.
Ciliary or ciliary body. Location: central zone of the middle ocular membrane. Outwardly it looks like a circular roller. The structure is slightly thickened.
The vascular part of the eye - processes, carry out the formation of ocular fluid. Special ligaments attached to the vessels, in turn, fix the lens.
Choroid. Posterior zone of the medial shell. It is represented by arteries and veins, with their help the other parts of the eye are supplied with food.
Inner lining of the eye– retina. The thinnest of all three shells. Presented different types cells: rods and cones.
It should be noted that peripheral and twilight vision humans are possible due to the fact that the shell contains rods and has high photosensitivity.
Cones are responsible for central vision. In addition, thanks to cones, a person has the ability to distinguish colors. The maximum concentration of these cells occurs in the macula or corpus luteum. The main function of this zone is to ensure visual acuity.
Ocular nucleus (eye cavity). The core consists of the following components:
- fluid that fills the chambers of the eye;
- lens;
- vitreous body.
The anterior chamber is located between the iris and cornea. The cavity between the lens and the iris is the posterior chamber. The two cavities have the ability to interact using the pupil. Thanks to this, intraocular fluid easily circulates between the two cavities.
Lens. One of the components of the ocular nucleus. Located in a transparent capsule, the location of which is the anterior zone of the vitreous body. Externally similar to a biconvex lens. Nutrition is carried out through the intraocular fluid. Ophthalmology identifies several important components lens:
- capsule;
- capsular epithelium;
- lens substance.
The lens and vitreous body are separated from each other over the entire surface the thinnest layer liquids.
Vitreous body. Occupies the largest part of the eye. The consistency resembles a gel. Main components: water and hyaluronic acid. Provides nutrition to the retina and is part of the optical system of the eye. The vitreous body consists of three components:
- the vitreous body itself;
- limiting membrane;
- Klyuev channel.
In this video you will see the principle of the human eye.
Eye protection system
Eye socket. Niche formed bone tissue, where the eye is directly located. In addition to the eyeball, it consists of:
- optic nerves;
- vessels;
- fat;
- muscles.
Eyelids. Folds formed by skin. The main task is to protect the eyes. Thanks to the eyelids, the eye is protected from mechanical damage and foreign bodies. In addition, the eyelids distribute intraocular fluid over the entire surface of the eye. The skin of the eyelids is very thin. Over the entire surface of the eyelids with inside the conjunctiva is located.
Conjunctiva. Mucous membrane of the eyelids. Location: anterior zone of the eye. Gradually transforms into conjunctival sacs without affecting the cornea of the eye. In the closed position of the eyes, with the help of the conjunctival leaves, a hollow space is formed, protecting against drying out and mechanical damage.
Lacrimal system of the eye
Includes several components:
- lacrimal gland;
- lacrimal sac;
- nasolacrimal duct.
The lacrimal gland is located near the outer edge of the orbit, in the upper zone. The main function is the synthesis of tear fluid. Subsequently, the liquid follows excretory ducts and, washing the outer surface of the eye, accumulates in the conjunctival sac. On last stage fluid collects in the lacrimal sac.
Muscular apparatus of the eye
The rectus and oblique muscles are responsible for eye movement. The muscles originate in the orbit. Following along the entire eye, the muscles end in the white.
In addition, this system contains muscles that allow the eyelids to close and open - the levator palpebral muscle and the orbicularis or orbital muscle.
Photo of the structure of the human eye
A diagram and drawing of the structure of the human eye can be seen in these pictures:
