The structure of the human eye

As the well-known Russian proverb says, "the eyes are the mirror of the soul." On them you can read the character of a person. Through the eyes, people see the world, see the beautiful things that are happening around them.

How is this wonderful organ arranged? What is the structure of the eye?

The central part of the eye is the eyeball. It is connected to the brain by a special optic nerve. The eyeball is shaped like an oval. It consists of the front and rear poles, which are connected by a straight line - the optical axis. The length of the optical axis in a healthy person is 24 mm. The ocular equator dividing the eyeball into two parts is slightly shorter than the optical axis. Its length is 23.6 mm. The vertical diameter of the eyeball is 23.3 mm. The eyeball has three shells, which protect its core from negative influences from the outside. This is the outer fibrous membrane, the middle choroid and the inner retina of the eye. The cornea-scleral capsule performs a protective function: it does not allow foreign bodies to penetrate to the lens and vitreous body. The thickness of the cornea varies from 0.6 mm to 1 mm in different places. According to its optical indices, it is the strongest refractive index. The structure of the eye is laid down so that the cornea does not contain blood vessels. But it contains a large number of nerve endings. It is thanks to the hypersensitivity of the sclera that a person blinks and blinks at the slightest danger to the eye. The sclera from the outside of the eye in thickness reaches 1 mm., While on the inside it is very thin. Its circular sinus regulates the outflow of intraocular fluid.

The structure of the eye is laid in such a way that normal eye pressure is always maintained. The space behind the cornea is filled with chamber moisture, which in its biochemical composition is similar to cerebrospinal fluid. The back wall of the anterior chamber of the eye is the iris, on which the pupil is. Iris contains pigments responsible for eye color. The symptom of eye color is transmitted genetically, and the dark color of the eyes is a dominant sign in relation to the light. More precisely, the dominant feature is the presence of pigment, and blue or light brown eyes are possible with a small content of this pigment. If the pigment is not present at all, then the person is an albino. Blood vessels give the white eye a pinkish hue. In the iris are two muscles responsible for the size of the pupil. When the light is bright, the pupil decreases, and in the dark, on the contrary, it becomes wider. The ciliary body is responsible for the production of intraocular fluid.

The structure of the eye is completely from the point of view of optical physics. It is amazing that nature has created such a sensitive mechanism, which it is still not possible to copy to mankind. The retina has ten layers. It is she who is responsible for the formation of the image and the perception of colors and shades. On how healthy the retina, depends on the number of shades differentiated by man. The cone and rod receptors consist of four parts: the outer segment, the constriction, the inner segment and the synaptic region. Rods are more sensitive to light due to the pigment of rhodopsin, and cones with iodopsin better fix movement. It is noteworthy that in many representatives of the animal world the structure of the eye provides only the presence of rods, but not cones.

To study the biophysical nature of vision, the structure and functions of the eye must be considered in conjunction with the structure of nerve cells and endings that transmit information from the retina to the occipital lobe of the brain. From the central region of the nerve disk of the eye, the vein and artery exit. The image transmitted by the left eye is formed in the right side of the brain, and the image fixed by the right eye is in the left.

This article, describing the structure of the eye, contains only general facts. If you want to understand the detailed structure of the organs of vision and the principles of their functioning, you will have to read countless number of reference books and textbooks on ophthalmology.