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The eye is one of the most complex organs in the body. Thanks to it, the image that is processed in it goes to the brain. 80% of all stimuli is provided by the eye. The organ is also responsible for proper motor coordination, color recognition and balance.
How is the human eye structured?
In appearance, the eye resembles a ball and consists of the eyeball, the eye’s locomotor apparatus and the protective apparatus. The radius of the eyeball is about 11 m; a volume of about 7 cm3; weight about 7 g. The organ consists of outer, middle and inner membranes. It is in the eyeball that the light is transformed and the image is formed. The structure of the eye is quite complicated. The outer layer consists of 5 sclera to which the muscles of the eyeball are attached.
The eyeball movement apparatus enables the eyeball to rotate within the orbit. Thanks to it, the eyeballs can assume a specific position and perceive visual sensations. The pupil diameter is variable and depends on the strength of the light rays that fall on the retina. Its size also depends on the observed object – the closer the object is, the smaller the pupil diameter. The eye of animals is built differently, e.g. a goat on the horizontal pupils.
The last element to mention when discussing the structure of the eye is the protective apparatus. It includes: eyelids, browbones, eyelashes, lacrimal organ and conjunctiva of the eyeball. The eyelids, made of flexible skin folds, protect the eye against too strong light stimuli; the lacrimal gland secretes a secretion that cleans and moisturizes the eye; eyelashes protect the eye from dust and dirt – there are about 250 on the upper eyelid and 150 on the lower eyelid.
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Eye – functions
The structure of the eye is an issue that is still being researched. The organ in question consists, inter alia, of from the following:
- sclera – this is a thick, white protective layer that gives the shape of the eyeball. It is she who surrounds the eye from the side of the eye sockets. Its thickness at the point where it passes into the sheath of the optic nerve is approximately 1,3 mm. The discussed eye structure element is poorly vascularized. The sclera protects the eye from injury. Its color suggests a person’s health condition – e.g. yellow sclera means problems with cholesterol.
- iris – lies between the lens and the cornea. This element of the structure of the eye is opaque and consists of many layers, with the pupil in the center. The iris also contains dye granules and blood vessels. What color it has depends on the dye it contains. In addition, it also contains two systems of muscle fibers. Thanks to the iris, the amount of light rays that enter the retina of the eye is controlled.
- lens – it is an element of the human eye located between the vitreous body and the iris, which focuses light rays. The lens is not innervated and is held in place by muscles and ligaments. Its shape depends on the species. Humans have disc-shaped lenses, and rodents have spherical lenses. Thanks to the lens, we can see objects in sharp shapes.
- the cornea – it is through it that light enters the eye. The cornea refracts the light rays and focuses them more strongly than the lens. This element of the human eye consists of anterior and posterior epithelium; anterior and posterior border lamina; Duy layer and from the essence. In addition, various chemicals can be absorbed into the body through the cornea.
In addition to the above-mentioned elements of the human eye, the aqueous humor, i.e. the substance filling the eye chamber, should also be considered; the vitreous body, a substance with a jelly-like consistency located between the lens and the back of the eyeball; the macula, i.e. the element of the retina with the highest resolution of vision; blind spot, i.e. the places on the retina without receptors where the optic nerve runs towards the brain. This is how the human eye is built.
Are you looking for ways to support the work of the eye? Omega acids, which can be found in the Omega 3-6-9 dietary supplement, have a beneficial effect on the support of the organ of vision. The ingredients of the preparation come from fish and vegetable oil.
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The structure of the eye and the process of seeing
The light first goes to the cornea, which is one of the main parts of the eye along with the lens. It is worth adding that the breaking force of the cornea is constant and amounts to 42 diopters, while the refraction of the lens is variable. The process is performed by the muscles that change the curvature of the lens. However, only some of the light that enters the cornea also goes to the lens. This is because a piece of light is “blocking” the sclera. Moreover, the amount of light hitting the retina is regulated by the pupil.
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The light is absorbed by the retina, which is made possible by its suppositories and rods, found in the yellow macula, located in the receptor epithelium. Thanks to them, we are able to distinguish, for example, black from white. This eye function is also responsible for twilight vision. The retina of the eye is connected to the cortex of the cerebral hemispheres. The eyes have optic nerves that cross each other. We divide the visual cortex into left and right.
The human eye has many functions. The process of seeing consists, inter alia, on distinguishing colors and shapes, determining the direction of studying light and distinguishing light from dark. This function can be performed by the eye in the photocepetors, the aforementioned rods and suppositories. The mechanism of vision in humans is slightly different than in animals. For example, some animals better recognize the linear polarization of light. The field of medicine that studies the structure and function of the eyes is ophthalmology.
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Eyes of animals and people – structure and functions
The working pattern of the human eye and the animal eye is similar, but they differ in several respects. Many people think that dogs, for example, cannot distinguish between colors, as they can only see in black and white. However, this is not true. A dog’s eye perceives individual colors, but not as accurately as a human eye. Quadrupeds perceive the world primarily in yellow and blue. Cats, on the other hand, see very well in the dark thanks to the fact that they have an elliptical pupil.
The scheme of how the eye of a fish works is interesting. These animals do not have lids, and their pupils do not constrict and dilate. Deep-sea species have two lenses – one facing up and the other facing down. Fish cannot see at long distances because they are short-sighted. On the other hand, the eyes of birds allow wide observation. The human eye is constructed in such a way that it cannot see in ultraviolet light, which in turn is accessible to birds. In addition, birds have a shimmer, that is, the third eyelid.
Structure of the eye – distinguishing colors
The ability to distinguish colors only develops over time. Not everyone knows that children see fewer colors than adults, although this is a larger palette than just black and white. This is due to the fact that the color receptors in the eye of a little person are still too weak, although newborns can already perceive shades of red. Interestingly, a two-month-old baby is already able to distinguish green from red, and over time is getting better at recognizing colors. When she is six months old, she recognizes colors just like an adult.
The human eye has receptors thanks to which we can recognize as many as 160 colors. What’s more, thanks to it we will also recognize several hundred thousand shades of individual colors.
Structure of the eye – reactions to light
Everyone knows that the pupil in the human eye reacts to light, but not everyone knows that it also reacts to emotions. People with this knowledge can read other people’s emotions precisely by the shape of their pupils. For example, a dilated pupil shows that a person is afraid, touched and even feels fear. The reduction of the pupils occurs when we feel uncomfortable.
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Structure of the eye – eye hazards
The human eye is a delicate organ. When the air in the room is low in humidity, tears, which are a natural shield against pollution, evaporate from the eyeballs faster. This leads to pain in the eyes that are itchy and red and therefore more prone to disease. It is advisable to regularly ventilate the rooms in which we stay on a daily basis. It’s a good idea to use an air humidifier and drink about 2 liters of water a day.
Another risk is excess ultraviolet radiation. This damages the cells of the retina, which can lead to conditions such as eye melanoma and cataracts. The brighter our eyes are, the more we are exposed to the harmful effects of the sun – for example, blue iris has the least pigment. In order to minimize the risk on sunny days, you should wear sunglasses with a UV 400 filter. It is also worth buying them for your child. It is advisable to buy glasses with large frames that will protect your eyes from side rays.
The eyes of a person are very much harmed by cigarette smoke. Smokers often suffer from dry eye syndrome. This is due to the toxins in cigarettes that damage the blood vessels of the eyeball. That is why smokers are more likely to suffer from cataracts, for example. Passive smokers are equally susceptible to the above-mentioned threats. The best way to avoid infection is to quit or at least use moisturizing drops.
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