Vision is the most important analyzer that allows a person to perceive about 80% of information about the outside world. A person who has never experienced vision problems rarely thinks about how one of the most important mechanisms in his body works.
Eyeball
The complex structure of the human eye allows us to distinguish colors, distances to objects, their shape and other aspects that are essential in the perception of the outside world. During normal operation of the eye apparatus, all layers of the eyeball must perform their specific functions.
Information is perceived by the peripheral part of the visual system, which also includes protective mechanisms:
- Eye socket.
- Or rather the eyelid.
- Lower eyelid.
The eyeball itself is located directly in the eye socket and is surrounded by muscle fibers, nerve plexuses and fiber. Three shells are distinguished in the structure of the eye:
- Fibrous sheath (outer).
- Vascular (medium).
- Photosensitive (internal).
Essence of the fibrous membrane
The outer shell of the eyeball is a kind of front part of the eye, which is also divided into two sections:
- The first transparent, which is called the cornea.
- The second, which occupies most of the whitish color, which is commonly called the sclera.
A circular sulcus of the sclera passes between the indicated departments.
The fibrous membrane of the eye consists of fairly dense connective fibers. Due to the density and elasticity of both the cornea and sclera, they allow the eye to be shaped.
The structure of the cornea
The transparent layer of the fibrous membrane, called the cornea, is only a fifth of the entire outer layer. The cornea itself has a transparent consistency, and forms a limbus at the point of its transition to the sclera.
The shape of the cornea is an ellipse with a diameter of about 12 mm and a layer thickness of only 1 mm. This shell has absolutely no vessels, is absolutely transparent, and all its cells are optically oriented. It is believed that the cornea of the eye grows to the size characteristic of an adult by the age of 10-12.
Despite its subtlety, this part of the fibrous membrane is divided into several layers:
- Epithelial.
- Bowman shell.
- Stroma (the thickest layer of the cornea of the eye).
- Descemet's shell.
- Posterior epithelial layer.
The structure of the fibrous membrane is arranged in such a way that inThe cornea contains a huge number of nerve receptors, so it is extremely sensitive to external influences. The cornea transmits light, but due to its refractive power, it modifies and refracts the rays.
There are no blood vessels in this layer, for this reason all metabolic processes are very slow.
Functions of the cornea
It is customary to distinguish two main functions that the layer of the cornea of the eye performs:
- Protective function. The high strength of the cornea, together with increased sensitivity and rapid regeneration of the upper layer of the epithelium, allows the cornea to fully cope with the task assigned to it.
- Light transmission and light refraction. Acting as an optical medium, due to its shape and transparency, it ensures the correct refraction of light rays. The degree of this refraction depends on the individual characteristics of the person.
What is the sclera?
The second important part of the fibrous membrane of the eyeball is the sclera, or as it is commonly called, the albuginea. Due to its density, it helps to maintain the necessary shape of the eyeball and protects its inner contents.
In a he althy state, this layer has a whitish tint and is colloquially called the “eye protein”.
The eye muscles are attached to the sclera. The thickness of the layer is heterogeneous, but sufficient to perform surgical manipulations without piercing the sclera through and through.
The whole layer consists of dense fibrousfabric with a high degree of elasticity. It contains a large number of collagen fibers, which are oriented parallel to the equator in the anterior part of the layer, and acquire a loop-like shape in the deeper layers.
The blood supply of the sclera is poor, it does not contain a large number of blood vessels. In contrast to the cornea, there are practically no nerve endings in the tunica albuginea and its sensitivity is extremely low, which increases the risk of developing pathological processes in this part of the eyeball.
When performing any surgical procedures on the eye, it must be taken into account that four important vorticose veins pass through the sclera.
Functions of the sclera
For the full operation of the eye apparatus, the functions of the fibrous membrane in the part of the sclera are as follows:
- Protective. It is considered that this function is the main one. The sclera allows you to protect other layers of the eyeball from external influences, including mechanical damage.
- Frame. The structure of the sclera supports the spherical shape of the eyeball. It is to it that ligaments, nerve endings, blood vessels and muscles are attached, which are also responsible for the synchronism of the eyes.
- Optical. Unlike the cornea, the sclera is opaque, which limits the amount of light reaching the retina. This provides a person with a good level of vision.
- Stabilization. The sclera layer is directly involved in the stabilization of eye pressure, which affects the work of all departments of the eye.apples. With constant changes in intraocular pressure, the collagen fibers of the sclera wear out.
