Suzanne D'Anna1 Anatomy of the Eyeball. Suzanne D'Anna2 Cavities of the Eyeball separated by the lens n anterior n posterior

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Suzanne D'Anna1 Anatomy of the Eyeball Slide 2 Suzanne D'Anna2 Cavities of the Eyeball separated by the lens n anterior n posterior Slide 3 Suzanne D'Anna3 Anterior Cavity n between lens and cornea n filled with aqueous humor (watery fluid) n Divided into: - anterior chamber (anterior to iris) - posterior chamber (posterior to iris) Slide 4 Suzanne D'Anna4 Posterior Cavity n between lens and retina n filled with vitreous body (jelly-like substance) n also called vitreous chamber Slide 5 Suzanne D'Anna5 Lens n elastic, transparent, biconcave structure n separates anterior and posterior cavities of eyeball n suspended from ciliary body by suspensory ligaments n tension on suspensory ligaments controls shape of lens Slide 6 Suzanne D'Anna6 Layers of Eyeball (tunics) n fibrous - outer - sclera - cornea n vascular - middle - choroid - ciliary body - iris n retina - inner nervous Slide 7 Suzanne D'Anna7 Layers of Eyeball pupil cornea ciliary body sclera choroid iris retina Slide 8 Suzanne D'Anna8 Slide 9 9 Sclera - outer fibrous n white of the eye n outermost n protects eye n thick, tough connective tissue n capsule that maintains shape of eye n serves as point of attachment for extrinsic muscles n makes up 5/6 of sclera Slide 10 Suzanne D'Anna10 Cornea - outer fibrous n anterior 1/6 of fibrous tunic; continuous with sclera n bulges forward, forming convex surface - refracts light rays as they enters eye n transparent - allows light rays to pass n lacks blood vessels n receives nutrition from lymph n has five layers Slide 11 Suzanne D'Anna11 Cornea - outer fibrous (cont.) n has touch and pain receptors n injury causes scarring n most exposed part of eye n great ability to repair itself n only tissue that can be transplanted from person to person without rejection Slide 12 Suzanne D'Anna12 Scleral Venous Sinus n also called canal of Schlemm n junction of sclera and cornea n drains aqueous humor from eyeball Slide 13 Suzanne D'Anna13 Choroid - middle vascular layer n vascular layer; blood rich n contains dark pigment produced by melanocytes - absorbs pigment and prevents scatter of light after it passes through retina n anterior portion becomes ciliary body and iris Slide 14 Suzanne D'Anna14 Ciliary Body - middle vascular layer n thickest part of vascular tunic n forms internal ring in anterior part of eyeball n within are projections or folds called ciliary muscles - secrete aqueous humor into anterior cavity n lens is attached via suspensory ligaments Slide 15 Suzanne D'Anna15 Iris - middle vascular layer n extends out from ciliary body n anterior to lens n thin diaphragm of connective tissue n seen from outside as colored portion of eye n has rounded opening called pupil n regulates amount of light entering posterior cavity of eyeball through pupil Slide 16 Suzanne D'Anna16 Pupils n bright light or close up - pupils constrict n dim light or distance - pupils dilate Slide 17 Suzanne D'Anna17 suspensory ligaments lens anterior chamber posterior chamber cornea pupil iris Slide 18 Suzanne D'Anna18 Retina - inner nervous layer n light sensitive n is where light rays form an image n image travels via optic nerve to cerebral cortex n if image is not focused correctly, corrective glasses or lenses are required n contains photoreceptors - rods and cones Slide 19 Suzanne D'Anna19 Photoreceptors n rods - 20 million - recognize gray tones and dim light n cones - 6 million - recognize primary colors n together they interpret intermediary colors n in moonlight only rods are functioning; therefore we cannot see colors Slide 20 Suzanne D'Anna20 Fovea Centralis n depressed area in center of macula lutea - yellowish spot just lateral to optic axis of eyeball n has highest concentration of cones in retina n produces sharpest vision and best color perception Slide 21 Suzanne D'Anna21 Optic Disc n also called blind spot n medial to optic axis n fibers from ganglion cells exit eyeball to form optic nerve n no photoreceptors; light striking this area produces no image Slide 22 Suzanne D'Anna22 Color Blindness n inability to distinguish colors n caused by a lack or deficiency in one of the three cone photopigments n most common type is red-green color blindness n inherited condition affecting males more often than females - sex-linked Slide 23 Suzanne D'Anna23 Intraocular Pressure n caused when scleral venous sinus is obstructed and reabsorption of aqueous humor cannot keep up with its secretion n pressure in chambers pushes lens back and puts pressure on vitreous body which in turn presses on retina which obstructs blood supply Slide 24 Suzanne D'Anna24 Intraocular Pressure (cont.) n retinal cells die and optic nerve may atrophy causing blindness (glaucoma) n symptoms usually go unnoticed until damage is irreversible n disease can be detected by use of tonometer used to measure intraocular pressure Slide 25 Suzanne D'Anna25 Glaucoma n group of eye diseases n characterized by an increase in intraocular pressure n pressure causes pathological changes in optic disk and visual field defects Slide 26 Suzanne D'Anna26 Normal Flow of Intraocular Fluid Slide 27 Suzanne D'Anna27 Abnormal Flow of Intraocular Fluid (most common type) n egress is partially blocked causing increased accumulation of fluid causing increase pressure and eventual blindness Slide 28 Suzanne D'Anna28 Acute Closed-Angle Abnormal Flow of Intraocular Fluid n egress is totally blocked causing permanent blindness suddenly Slide 29 Suzanne D'Anna29 Accessory Structures n eyelids n lacrimal apparatus n extrinsic muscles n cranial nerves Slide 30 Suzanne D'Anna30 Eyelid n Composed of: - skin covers outer surface - conjunctiva covers inner surface of eyelid and anterior surface of eyeball (except cornea) Slide 31 Suzanne D'Anna31 Eyelid (cont.) n Composed of: - tarsal glands modified sebaceous gland (oil) open at edge of each eyelid also called Meibomian glands - muscles orbicularis oculi - surrounds eye levator palpebrae - in upper eyelid Slide 32 Suzanne D'Anna32 Lacrimal Apparatus n lacrimal gland n superior and inferior canaliculi n lacrimal sac n nasolacrimal duct Slide 33 Suzanne D'Anna33 Lacrimal Gland n located in upper portion of each orbit n secretes constant flow of tears - wash anterior surface of eyeball - maintain moist and clean environment for cornea and conjunctiva - contain antibacterial enzyme lysozyme that helps prevent eye infections Slide 34 Suzanne D'Anna34 Superior and Inferior Canaliculi n collect tears after they have washed over eyeball Lacrimal Sac n collects tears from canaliculi Nasolacrimal Duct n connects lacrimal sac to nasal cavity where tears are swallowed Slide 35 Suzanne D'Anna35 Extrinsic Muscles n arise from bones of the orbit n inserted into broad tendons on sclera n Six extrinsic eyeball muscles: lateral rectusmedial rectus superior rectusinferior oblique inferior rectussuperior oblique Slide 36 Suzanne D'Anna36 superior oblique trochlea superior rectus lateral rectus (cut) inferior oblique medial rectus inferior rectus Slide 37 Suzanne D'Anna37 Primary Actions of the Eye Muscles n abduction n adduction n elevation n depression Slide 38 Suzanne D'Anna38 Abduction n contraction of lateral rectus moves pupil away from nose Adduction n contraction of medial rectus moves pupil towards nose Slide 39 Suzanne D'Anna39 Elevation n contraction of superior rectus or inferior oblique muscles moves pupil upward Depression n contraction of inferior rectus or superior oblique muscles moves the pupil downward Slide 40 Suzanne D'Anna40 Cranial Nerves of Eyeball Innervation n oculomotor (III) - branches innervate superior rectus, medial rectus, inferior oblique, and inferior rectus n trochlear (IV) - innervates superior oblique n abducens (VI) - innervates the lateral rectus

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