Describe the three layers of the eye and the functions of each layer.
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The eye has three layers: 1) the corneal/sclera layer or fibrous tunic; 2) the uveal layer or vascular tunic and 3) the retina or neural tunic (Slomianka, 2009; The University of Michigan Medical School (UMMS), 2005).
The fibrous tunic is the outer layer and forms a capsule around the eye protecting the inner parts of the eye (Slomianka, 2009). It has two main components, the sclera and the cornea.
The sclera covers 5/6 of the eye and its primary function is structural. It is made of a collagenous fibers and elastic fibers that form a dense connective tissue where the ocular muscles attach (Slomianka, 2009). The connective tissue expands or adapts to the changes in pressure inside the eye.
The cornea occupies the anterior most 1/6 of the tunica externa (UMMS, 2005). Its diameter is ~11 mm (Slomianka, 2009). The cornea functions are to admit and refract light (Bloodgood, 2003). The cornea has five layers, three cellular layers separated by two acelullar layers. The anterior and outermost layer of the cornea is the corneal epithelium, a stratified, non-keratinized epithelium that unites with the sclera (UMMS, 2005). It is followed by the first acelullar layer called the Bowman's membrane that serves as basement membrane to the epithelium (Bloodgood, 2003). The next layer is the stroma which makes much of the cornea and is responsible for its transparency (UMMS, 2005). A cellular layer called the Descemet's membrane follows the stroma and serves as a basement membrane to the last layer of the cornea the endothelium (UMMS, 2005). The endothelium lines the surface of the cornea exposed to the anterior chamber (Bloodgood, 2003). It is responsible for maintaining the correct hydration to the stroma, and has limited proliferative potential which accounts for the need for transplantation to correct any damage it suffers (UMMS, 2005).
The uveal layer or vascular tunic has three main components, the choroid, ciliary body and the iris (Slomianka, 2009; UMMS, 2005). The choroid consists of connective tissue divided in three layers. Its outer layer closest to the stroma has melanocytes (melanocyte layer) which gives the choroid a dark color ...
The solution involves a description of the three layesr of the eye has three layers: the corneal/sclera layer or fibrous tunic, the uveal layer or vascular tunic, and the retina or neural tunic.