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The uvea (/ ˈ j uː v i ə /; [1] derived from Latin: uva meaning "grape"), also called the uveal layer, uveal coat, uveal tract, vascular tunic or vascular layer, is the pigmented middle layer of the three concentric layers that make up an eye, precisely between the inner retina and the outer fibrous layer composed of the sclera and cornea.
It consists of dense connective tissue filled with the protein collagen to both protect the inner components of the eye and maintain its shape. [ 5 ] The vascular tunic, also known as the tunica vasculosa oculi or the "uvea", is the middle vascularized layer which includes the iris , ciliary body , and choroid .
The sclera and cornea form the fibrous tunic of the bulb of the eye; the sclera is opaque, and constitutes the posterior five-sixths of the tunic; the cornea is transparent, and forms the anterior sixth. The term "corneosclera" is also used to describe the sclera and cornea together. [1]
The ciliary body is a ring-shaped thickening of tissue inside the eye that divides the posterior chamber from the vitreous body. It contains the ciliary muscle, vessels, and fibrous connective tissue. Folds on the inner ciliary epithelium are called ciliary processes, and these secrete aqueous humor into the posterior chamber. The aqueous humor ...
The eye can be considered as a living optical device. It is approximately spherical in shape, with its outer layers, such as the outermost, white part of the eye (the sclera) and one of its inner layers (the pigmented choroid) keeping the eye essentially light tight except on the eye's optic axis.
The human choroid is thickest at the far extreme rear of the eye (at 0.2 mm), while in the outlying areas it narrows to 0.1 mm. [1] The choroid provides oxygen and nourishment to the outer layers of the retina. Along with the ciliary body and iris, the choroid forms the uveal tract.
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The pars plana (also known as orbicularis ciliaris [1]) (Latin: flat portion) is part of the ciliary body in the uvea (or vascular tunic, the middle layer of the three layers that comprise the eye). It is about 4 mm long, located near the junction of the iris and sclera, and is scalloped in appearance.