Accommodation apparatus of eye
Accommodative apparatus of the eye (iris, ciliary body with ciliary girdle) provides a change in the shape and refractive power of the lens, focusing the image on the retina, as well as the adaptation of the eye to the light intensity.
Iris (iris, iris). Is a disk-formation with a hole in the center of Variability - pupil, "apple of his eye." It is a derivative of the vascular (mostly) and the mesh membranes. Behind the iris pigment epithelium is covered by the retina. Located between the cornea and the lens on the border between the anterior and posterior chamber of the eye. The edge of the iris, connecting it to the ciliary body, called the ciliary margin. Iris stroma consists of loose fibrous connective tissue rich in pigment cells. Here are smooth muscle forming muscle, narrowing and expanding the pupil (m. sphincter pupillae, m. Dilatator pupillae).
In iris distinguish five layers: the anterior epithelium that covers the front surface of the iris, the outer boundary (avascular) layer, vascular layer, the inner boundary layer and the pigment epithelium.
Iris carries out its function as a diaphragm with two eye muscles: narrowing a (musculus sphincter pupillae) and expanding (musculus dilatator pupillae) pupil.
Ciliary body (corpus ciliare). Ciliary body is derived vascular and reticular membranes. Performs the function of fixing the lens and changing its curvature, thus engaging in an act of accommodation. The ciliary body is divided into two parts: internal - ciliary crown (corona ciliaris) and outside - the ciliary ring (orbiculus ciliaris).
Distinguish external meridional muscle bundles lying directly below the sclera, the average radial and circular muscle bundles, forming a ring muscle layer. Between the muscle bundles is loose fibrous connective tissue with pigment cells. Reduction of ciliary muscle relaxation leads to a circular fiber bundles - ciliary girdle of the lens, so that the lens becomes convex and its refractive power increases.
Ciliary body and ciliary processes covered ciliary part of the retina. The last layer is represented by a cubic intensely pigmented epithelium. Epithelial cells covering the ciliary body and processes, involved in the formation of aqueous humor that fills both of the eye.
Choroid (choroidea, mouth.: Uvea) operates the RPE and photoreceptors, regulates the pressure and temperature of the eyeball. This highly pigmented vascular tissue (rich in melanocytes), its thickness in the back field 0,22-0,3 microns, and at the periphery of 0.1-0.15 mm. There are 4 layers above-vessels, vascular, vascular and capillary plate and the basal complex.
Above-vessels plate (lamina suprachoroidea) thickness of 30 microns is the outermost layer of the choroid, adjacent to the sclera. It is formed by loose fibrous connective tissue, contains a large number of pigment cells (melanocytes), collagen fibers, fibroblasts, blood vessels and nerve plexus.
Vascular plate (lamina vasculosa) consists of intertwined arteries and veins between which the loose fibrous connective tissue, pigment cells, the individual bundles of smooth muscle cells.
Vascular capillary plate (lamina choroicapillaris) horoidei contains gemokapillyary visceral or sinusoidal type, from an uneven caliber. Between capillaries are flattened fibroblasts.
Basal complex (complexus basalis) - Bruch's membrane (lamina vitrea, lamina elastica, membrana Brucha) - a very thin plate (1-4 mm), located between the choroid and the pigment layer (epithelium) of the retina. It distinguishes the outer layer of collagen with a zone of thin elastic fibers, and the extension of the fiber-vascular capillary plate, inner layer of collagen, a fibrous (fibrous), wider, and the third layer is represented by the basement membrane of pigment epithelium – cuticular.
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