B. Choroid. It is the clear, transparent front part of the eye that covers the iris, pupil and anterior chamber and provides most of an eye’s optical power (if too flat = hyperopia/farsightedness; if too steep = myopia/nearsightedness). Together with the cornea and aqueous humor, the vitreous body and lens belong to the refractive media of the eyeball. The optic nerve from each eye divides in the optic chiasm. The cornea and the lens help to focus the light rays onto the back of the eye (retina). The size of the pupil is controlled by the action of the pupillary sphincter muscle and dilator muscle. It provides attachment surfaces for eye muscles Choroid The colorful structure of the eye that changes the shape of the pupil to allow for different amounts of light to enter the inner eye. Light enters the eye by passing through the transparent cornea and aqueous humor. The eye works much the same as a camera. Is the transparent, curved front of the eye which helps to converge the light rays which enter the eye Sclera Is an opaque, fibrous, protective outer structure. Near the front of the eye, in the area protected by the eyelids, the sclera is covered by a thin, transparent membrane ( conjunctiva ), which runs to the edge of the cornea. Fibrous Layer. Humans have two eyes, situated on the left and the right of the face. Iris: colored part of the eye that helps regulate the amount of light that enters. We shall now look at these layers in further detail. The conjunctiva also covers the moist back surface of the eyelids and eyeballs. The eye is the photo-receptor organ. Structure of Human Eye. The eyes sit in bony cavities called the orbits, in the skull. The sclera is outermost layer of the eyeball. The sclera is the outermost layer of tissue, also called the white of the eye. The nerve fibers from the photoreceptors are bundled together to form the optic nerve. The outer covering of the eyeball consists of a relatively tough, white layer called the sclera (or white of the eye). Anatomy of the Eye . The iris—the circular, colored area of the eye that surrounds the pupil—controls the amount of light that enters the eye. Through the action of small muscles (called the ciliary muscles), the lens becomes thicker to focus on nearby objects and thinner to focus on distant objects. There are 6 sets of muscles attached to outer surface of eye ball which helps to rotate it in different direction. It is soft connective tissue, and the spherical shape of the eye is maintained by the pressure of the liquid inside. The trusted provider of medical information since 1899, Muscles, Nerves, and Blood Vessels of the Eyes. Cornea - The cornea is the clear, dome-like structure on the front part of the eye.The cornea delivers 2/3 of the refracting power to the eye. We do not control or have responsibility for the content of any third-party site. So, this is called the cornea. The sclera. Thank you so much for sharing… https://t.co/OlTrNq9mi9, Modern slavery and human trafficking statement. Its wall has three distinct layers—an outer (fibrous) layer, a … It converts light into electrical impulses. It is filled with a fluid called the aqueous humor, which nourishes the internal structures. It is the white (and opaque) part of the eyeball. The back section (posterior segment) extends from the back surface of the lens to the retina. The outer covering of the eyeball consists of a relatively tough, white layer called the sclera (or white of the eye). Pupil. It contains a jellylike fluid called the vitreous humor. The role of refractive structures to bend the direction of the light that falls onto the eye and focus it onto the retina. It consists of the sclera and cornea, which are continuous with each other. It also has muscles that allow its accommodation within or on top of the head, depth perception, and true colour vision. Cones are responsible for sharp, detailed central vision and color vision and are clustered mainly in the macula. The legacy of this great resource continues as the MSD Manual outside of North America. Eye Anatomy Handout Author: National Eye Institute , National Eye Health Education Program Subject: Diabetes and Healthy Eyes Toolkit and Website Keywords: Eye anatomy, eye diagram, cornea, iris, lens, macula, optic nerve, pupil, retina, vitrous gel, diabetic eye disease. Each photoreceptor is linked to a nerve fiber. Lens. Just like a lens in a camera sends a message to produce a film, the lens in the eye 'refracts' (bends) incoming light onto the retina. The eyeball can be divided into the fibrous, vascular and inner layers. Normally, the aqueous humor is produced in the posterior chamber, flows slowly through the pupil into the anterior chamber, and then drains out of the eyeball through outflow channels located where the iris meets the cornea. The main parts of the human eye are the cornea, iris, pupil, aqueous humor, lens, vitreous humor, retina, and optic nerve. With age, the sclera becomes more yellow in colour. Rods are more numerous than cones and much more sensitive to light, but they do not register color or contribute to detailed central vision as the cones do. Each orbit is a pear-shaped structure that is formed by several bones. The inside of the eye contains the two refractive structures of the eye called the lens and vitreous body. A thin layer called the conjunctiva sits on top of this. The Eye - Science Quiz: Our eyes are highly specialized organs that take in the light reflected off our surroundings and transform it into electrical impulses to send to the brain. Structure of the Human Eye The eye is a hollow, spherical structure about 2.5 centimeters in diameter. This video covers the following syllabus objectives from Edexcel IGCSE Biology 9-12.91 Describe the structure and function of the eye as a receptor. The iris allows more light into the eye (enlarging or dilating the pupil) when the environment is dark and allows less light into the eye (shrinking or constricting the pupil) when the environment is bright. The inside lining of the eye is covered by special light-sensing cells that are collectively called the retina. It needs to be … There are six extraocular muscles that control eye movements. Thus, the pupil dilates and constricts like the aperture of a camera lens as the amount of light in the immediate surroundings changes. The front section (anterior segment) extends from the inside of the cornea to the front surface of the lens. This black area is actually a hole that takes in light so the eye … Vision occurs when light enters the eye through the pupil.  Gift of the Creator Gives us the sense of sight 70% of all sensory receptors are in the eye Spheroid structure, about 2/3 the size of aping-pong ball Functions: distinguishes light and dark,shape, colour, brightness & distance ofobjects. This layer is a very stable fibrous membrane that continues to retain the shape of the eye and provides protection. The front (anterior) chamber extends from the cornea to the iris. Light passes through the front of the eye (cornea) to the lens. It is composed of light sensitive cells known as rods and cones. Muscles responsible for moving the … From developing new therapies that treat and prevent disease to helping people in need, we are committed to improving health and well-being around the world. The retina coats the entire back of the eyeball. The link you have selected will take you to a third-party website. The human eye contains about 125 million rods, which are necessary for seeing in dim light. External components include: Sclera; Conjunctiva; Cornea; Iris; Pupil; Internal components include: The structures and functions of the eyes are complex. The iris controls the size of the pupil, which is … These layers have different structures and functions. The cells in the retina absorb and convert the light to electrochemical impulses which are transferred along the optic nerve and then to the brain. The pressure generated by these fluids fills out the eyeball and helps maintain its shape. Anatomy of the Eye. So once the light ray comes towards the back of the eye, it will hit a structure known as the retina. Each eye constantly adjusts the amount of light it lets in, focuses on objects near and far, and produces continuous images that are instantly transmitted to the brain. The middle of these fields of vision overlaps. 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