It is divided into orbital and palpebral portions, and it is essentially the palpebral portion, within the lid, that causes lid closure. The choroid supplies the outer retina with nutrients and maintains the temperature and volume  of the eye . Structure of Human Eye. The human eye is a roughly spherical organ, responsible for perceiving visual stimuli. The first thing we're going to draw is the white part of the eye, which is known as the sclera. The pyramidalis, or procerus, muscles occupy the bridge of the nose; they arise from the lower portion of the nasal bones and are attached to the skin of the lower part of the forehead on either side of the midline; they pull the skin into transverse furrows. It is a very important part of the eye, but you can hardly see it because it's made of clear tissue. And we're going to do that by drawing a cross-sectional diagram of the eyeball. When you talk of the human eye structure, they exist in pairs, each one being approximately 2.5 cm in diameter. It absorbs light rays from our environment and transforms them in such a way that the information in the brain can be processed it lies in the eye socket and is attachedto various muscles. A small, red portion of the corner of the eye that contains modified sebaceous and sweat … The palpebral portion passes across the lids from a ligament called the medial palpebral ligament and from the neighbouring bone of the orbit in a series of half ellipses that meet outside the outer corner of the eye, the lateral canthus, to form a band of fibres called the lateral palpebral raphe. The protrusion of the eyeballs—proptosis—in exophthalmic goitre is caused by the collection of fluid in the orbital fatty tissue. A horizontal cross section of the human eye, showing the major parts of the eye, including the protective covering of the cornea over the front of the eye. The conjunctiva lines the lids and then bends back over the surface of the eyeball, constituting an outer covering to the forward part of this and terminating at the transparent region of the eye, the cornea. The puncta are openings into the lacrimal ducts; these carry the tears into the lacrimal sacs, the dilated upper ends of the nasolacrimal ducts, which carry the tears into the nose. This is achieved by the eyelids, which during waking hours sweep the secretions of the lacrimal apparatus and other glands over the surface at regular intervals and which during sleep cover the eyes and prevent evaporation. Please select which sections you would like to print: Corrections? The sclera, also known as the white of the eye or, in older literature, as the tunica albuginea oculi, is the opaque, fibrous, protective, outer layer of the human eye … There are following main parts of human eye: Sclera: The knowledge of eye parts and functions is both useful and interesting. The skin of the forehead, temple, and cheek is then drawn toward the medial (nose) side of the orbit, and the radiating furrows, formed by this action of the orbital portion, eventually lead to the so-called crow’s feet of elderly persons. Two ligaments, the medial and lateral palpebral ligaments, attached to the orbit and to the septum orbitale, stabilize the position of the lids in relation to the globe. The portion that lines the lids is called the palpebral portion of the conjunctiva; the portion covering the white of the eyeball is called the bulbar conjunctiva. The eyeball and its functional muscles are surrounded by a layer of orbital fat that acts much like a cushion, permitting a smooth rotation of the eyeball about a virtually fixed point, the centre of rotation. The cornea (say: KOR-nee-uh), a transparent dome, sits in front of the colored part of the eye. These ligaments, control the shape of the eye & is continuous anteriorly with the transparent cornea for,... 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