the eye

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the eye the eye * definition organ of the sense of sight situated in the orbital cavity spherical 2.5 cm dia the space between the eye and the orbital cavity is occupied by fatty tissue; the bony wall and the fat protect the eye from injury. strucuturally separate; but certain activities are coordinated and function as a pair. two eyes  sense of depth and distance * * structure three layers in the wall outer fibrous layer : sclera and cornea middle vascular layer: choroid, ciliary body and iris the inner nervous tissue layer : retina. the structures inside the eyeball are the lens, aqueous fluid (humour) and vitreous body * sclera sclera = white portion of the eye outermost layer continuous with the cornea anteriorly firm fibrous membrane gives attachment to the extraocular muscles of the eye cornea continuation of the sclera anteriorly transparent convex epithelial membrane light rays …

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rture – pupil when iris contracts the pupil is constricted and when iris relaxes the iris is dilated – parasympathetic supply - oculomotor * lens highly elastic circular biconvex transparent body behind pupil suspended from the ciliary body by the suspensory ligament eclosed within a transparent capsule thickness controlled by the ciliary muscle contraction of the muscle moves the lens forward thereby reducing the pull on the lens and increasing the thickness of the lens * retina innermost layer stimulated by light rays several layers of nerve cell bodies and their fibres lying on a pigmented layer of epithelial cells the layer highly sensitive to light is thelayer is the layer of rods and cones. macula lutea fovea centralis – only cone shaped cells anteriorly there are fewer cones than rods contain photosensitive pigments convert light rays into nerve impulses. * optic nerve the nerve fibres originate in the retina …

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aintenance of the balance. * rhodopsin (visual purple) - degraded or bleached when exposed to light – regeneration requires vitamin a. the time taken for the regeneration of rhodopsin is called dark-adaptation other pigments present in cones respond to different wavelengths of visible ligt and are responsible for colour vision. 0.5 cm to the nasal side of the macula lutea all the nerve fibres of the retina converge to form the optic nerve which passes through the sphenoid bone  cerebral cortex in the occipital lobe of the cerebrum. optic disc or the blind spot – optic nerve leaves the eye. * 20 blood supply to the eye internal carotid artery through its branches- ophthalmic artery :- ciliary arteries – central retinal artery. venous drainage is by anumberof veins, central retinal vein  cavernous sinus. central retinal artery and vein are encased in the optic nerve. entering the eye at …

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d outwards inferior oblique – upwards and outwards voluntary muscles – needed for convergence and accommodation * nerve supply to the muscles of the eye extrinsic muscles superior rectus inferior rectus medial rectus inferior oblique intrinsic muscles iris ciliary muscle all of the above six muscles are supplied by oculomotor nerve superior oblique – trochlear nerve lateral rectus – abducent nerve * eye brows arched supra orbital protect the eye from sweat, dust, and other foreign bodies eye lids (palpebrae) movable folds of tissue upper and lower free edges have hair – eye lashes layers of the eyelids are: skin areolar tissue two muscles – the orbicularis oculi and levator palpebrae superioris tarsal plate – thin sheet of dense conective tissue a lining of conjuctiva * conjuntiva transparent membrane lining the eyelids and the front of the eyeball on the eyelids the conjunctiva has highly vascular epithelium corneal conjunctiva consists …

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canthus where it drains into two lacrimal canaliculi the opening of each is called the puncum the two canaliculi lie on lie one above the other separated by a small red body, the caruncle. the tears then drain into the lacrimal sac the upper end of the nasolacrimal duct nasolacrimal duct opens into the nasal cavity opening at the level of the inferior concha. * eye model nerves * eye model blood supply * eye model cross-section * eye model inside skull * * * * slide 4 * five back to slide 4 * * * the human eye works like a living camera. like a camera, the eye processes light and takes mental snapshots of images, which are then developed in the brain. in order to create vision, all parts of the eye must work together as a team. the cornea, the clear, film-like part of the eye, …

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О "the eye"

the eye the eye * definition organ of the sense of sight situated in the orbital cavity spherical 2.5 cm dia the space between the eye and the orbital cavity is occupied by fatty tissue; the bony wall and the fat protect the eye from injury. strucuturally separate; but certain activities are coordinated and function as a pair. two eyes  sense of depth and distance * * structure three layers in the wall outer fibrous layer : sclera and cornea middle vascular layer: choroid, ciliary body and iris the inner nervous tissue layer : retina. the structures inside the eyeball are the lens, aqueous fluid (humour) and vitreous body * sclera sclera = white portion of the eye outermost …

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