Iris. Features of the structure of the human eye

The iris is the anterior part of the choroid of the eye. It is a very thin peripheral component of it. She, the ciliary (ciliary) body and the choroid   Are the three main parts of the vasculature, formed during the period from four to eight months of intrauterine fetal development.

The iris is formed approximately to the seventeenth week in the place where the "overlap" of the mesoderm occurs on the edge of the so-called eye cup. By the fifth month, the sphincter of the iris is formed - the muscle responsible for the reduction in the size of the pupil. A little later, the dilator appears. This is the internal muscle, which will subsequently provide expansion. As a result of harmonious and harmonious interaction of the sphincter and dilator, the iris of the eye performs the function of the diaphragm, which effectively regulates the flow of penetrating light rays. By the sixth month, the back pigment epithelial tissue is completely formed . This concludes the basic processes of the formation of this system.

Immediate direct contact with the cornea iris of the person does not have. Between it and the outer wall remains a small space - the front chamber, which is filled with watery (chamber) moisture.

The iris itself looks like a rounded plate with a diameter of about twelve millimeters and a perimeter of about thirty-eight millimeters. In its center there is a round hole through which light penetrates, the pupil. It serves to regulate the volume of rays penetrating the eye. The size of the pupil depends on the degree of illumination. The smaller around the world, the greater will be its diameter. Its average size is about three millimeters. In young people, the diameter of the pupil is usually slightly larger than that of the elderly. This is due to the fact that dilator atrophy and fibrotic changes in the sphincter occur with time.

The main properties of such an eye element, as the iris, are the color, pattern, the state of the pupil opening and the location relative to other eye structures. All of them are due to certain anatomical characteristics of its structure.

The anterior layer of the iris has a radial striation, which gives it a peculiar lacy relief. Slot-like recesses located in its connective tissue are called lacunas. Retreating one or one and a half millimeters parallel to the pupillary margin, the mesentery is arranged (a dentate shaft). They divide the iris into two parts: the outer (ciliary) and the inner - the pupillary. The first zone defines concentric furrows. They are a direct consequence of the reduction and spreading of the iris as it moves.

The posterior part of the anterior part of the choroid is represented by a dilator with its pigment and border layers. The first at the pupillary margin forms a rim, or fringe. The anterior part of the iris includes the iris stroma and the outer boundary layer.