Eyeball Structure, Function & Muscles
Eyeball, spheroidal structure containing sense receptors for vision, found in all vertebrates and constructed much like a simple camera. Read the article to know more.
Nivedita Dar5 Aug, 2024
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The eyeball is a vital structure that facilitates vision. It is located in a bony cavity called the orbit. The eyeball has a light-focusing system that concentrates light on the receptor body known as the retina.
The retina helps us perceive light through electrochemical changes in the retinal pigment epithelium. This information is then transmitted to the brain, specifically to the occipital cortex. Structure of the Eyeball The eyeball consists of three layers: the fibrous layer, the vascular layer, and the inner layer. The Fibrous Layer This is the outermost layer. It consists of the sclera and cornea, which are continuous with each other. Their main functions are to provide shape to the eye and support the deeper structures. The cornea is transparent and positioned centrally at the front of the eye. Light entering the eye is focused by the cornea.The Vascular Layer
This layer lies beneath the fibrous layer. It consists of the choroid, ciliary body, and iris. Choroid : A layer of connective tissue and blood vessels that provides nourishment to the outer layers of the retina. Ciliary Body : Comprises two parts—the ciliary muscle and ciliary processes. The ciliary muscle consists of a collection of smooth muscle fibers. Iris : A circular structure with an aperture in the center (the pupil). The diameter of the pupil is altered by smooth muscle fibers within the iris.The Inner Layer
The inner layer of the eye is formed by the retina. Pigmented (outer) Layer : Formed by a single layer of cells. It is attached to the choroid and helps the choroid absorb light. Neural (inner) Layer : Consists of photoreceptors, the light-detecting cells of the retina.Extraocular Muscles
The extraocular muscles are responsible for the movement of the eyeball within the orbit. There are six extraocular muscles: the superior rectus, inferior rectus, medial rectus, lateral rectus, superior oblique, and inferior oblique. These muscles work in coordination to control the movements of the eye, allowing it to look in different directions. The superior rectus elevates the eye, while the inferior rectus depresses it. The medial rectus moves the eye inward, and the lateral rectus moves it outward. The superior oblique and inferior oblique muscles allow for rotational movements. Proper functioning of these muscles is essential for binocular vision and for maintaining the alignment of the eyes, which is crucial for depth perception and a single, coherent visual field.Eyeball FAQs
What is the macula?
The macula is the central area in the retina with maximum visual acuity due to the presence of a high concentration of cone cells.
What is the vitreous body?
The vitreous body is a transparent gel that fills the area posterior to the lens.
What is a cataract?
A cataract occurs when your eye's natural lens becomes cloudy. Proteins in your lens break down, causing things to look blurry, hazy, or less colorful.
What is glaucoma?
Glaucoma refers to a group of eye diseases that result in damage to the optic nerve and is associated with an increase in eyeball pressure.
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