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13. Special Senses: The Eye and the Ear. Multimedia Directory. Slide 14 Eye Anatomy Animation Slide 60 Optometrist Video Slide 68 Cataracts Video Slide 73 Macular Degeneration Video Slide 77 Conjunctivitis Video Slide 90 Snellen Chart Video Slide 115 Audiology Video
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13 Special Senses: The Eye and the Ear
Multimedia Directory Slide 14 Eye Anatomy Animation Slide 60 Optometrist Video Slide 68 Cataracts Video Slide 73 Macular Degeneration Video Slide 77 Conjunctivitis Video Slide 90 Snellen Chart Video Slide 115 Audiology Video Slide 117 Ear Anatomy Animation Slide 135 Inner Ear Anatomy Animation Slide 153 Otitis Media Video Slide 159 Tympanometry Video Slide 162 Audiometry Video
The Eye at a Glance • Function of the Eye • Contains sensory receptors for vision
The Eye at a Glance • Structures of the Eye • Sclera • Choroid • Retina • Eyeball • Conjunctiva • Eye muscles • Eyelids • Lacrimal apparatus
Eye Combining Forms • ambly/o – dull or dim • aque/o – water • blast/o – immature, embryonic • blephar/o – eyelid • chromat/o – color • conjunctiv/o – conjunctiva • corne/o – cornea • cycl/o – ciliary muscle
Eye Combining Forms • dacry/o – tear; tear duct • dipl/o – double • emmetr/o – correct, proper • glauc/o – gray • ir/o – iris • irid/o – iris • kerat/o – cornea • lacrim/o – tears
Eye Combining Forms • macul/o – macula lutea • mi/o – lessening • mydr/i – widening • nyctal/o – night • ocul/o – eye • ophthalm/o – eye • opt/o – eye, vision • optic/o – eye, vision
Eye Combining Forms • papill/o – optic disk • phac/o – lens • phot/o – light • presby/o – old age • pupill/o – pupil • retin/o – retina • scler/o – sclera • stigmat/o – point
Eye Combining Forms • uve/o – vascular • vitre/o – glassy
Eye Suffixes • –ician specialist • –metrist one who measures • –opia vision condition • –opsia vision condition • –tropia turned condition
Anatomy and Physiology • Ophthalmology (Ophth) is study of the eye • Eyeball • Organ of sight • Transmits external image using sensory impulses via optic nerve to brain • Brain translates sensory impulses into image
Anatomy and Physiology • External structures important for vision • In addition to eyeball • Eye muscles • Eyelids • Conjunctiva • Lacrimal apparatus
Eye Anatomy Animation Click on the screenshot to view an animation on the anatomy of the eye. Back to Directory
The Eyeball • Composed of three layers: • Sclera • Choroid • Retina
Sclera • Outermost layer • Tough protective layer • Another term for sclera is white of eye • Anterior portion is cornea
Cornea • Anterior portion of sclera • Clear, transparent • Allows light to enter • Bends, or refracts, light rays
Choroid • Middle layer • Provides blood supply for eye • Anterior portion: • Iris • Pupil • Ciliary body
Iris and Pupil • Iris • Colored portion of eye • Smooth muscle that changes size of pupil • Pupil • Opening in center of iris • Allows light to enter into eyeball
Ciliary Body and Lens • Lens • Behind iris • Not actually part of choroid layer • Attached to ciliary body
Ciliary Body and Lens • Ciliary body • Pulls on edge of lens • Changes shape of lens so it can focus light onto retina
Retina • Contains sensory receptor cells that detect light rays • Rods • Active in dim light • See gray tones • Cones • Active only in bright light • Color vision
Retina • Macula lutea • Area of retina where image forms • Fovea centralis • Depression in center of macula lutea • High number of cones • Point of clearest vision
Optic Disk • Point where the optic nerve leaves eyeball • Retinal blood vessels enter and leave through optic disk • No rods or cones • Results in blind spot in each eye’s field of vision
Figure 13.2Photograph of the retina of the eye. The optic disk appears yellow and the retinal arteries radiate out from it.(Photo Researchers, Inc.)
Eye Fluids • Aqueous humor • Watery fluid • Located between cornea and lens • Vitreous humor • Semi-solid gel • Located between lens and retina
Muscles of the Eye • Six muscles that connect eyeball to skull • 4 rectus muscles pull straight • 2 oblique muscles pull on an angle • Contract in combination to change direction in which each eye is looking
Eyelids • A pair cover each eyeball • Provide protection from foreign particles, injury, sun, and trauma • Both upper and lower edges have eyelashes or cilia that protect eye from foreign particles • Sebaceous glands located in eyelids secrete a lubricating oil onto surface of eyeball
Conjunctiva • A mucous membrane • Forms continuous covering on underside of each eyelid and across anterior surface of each eyeball • Protects eyeball
Lacrimal Apparatus • Lacrimal gland • Located under outer upper corner of each eyelid • Produces tears • Tears wash and lubricate anterior surface of eyeball
Lacrimal Apparatus • Lacrimal ducts • Located in inner corner of eye socket • Collect tears • Drain into nasolacrimal duct • Ultimately drain into nasal cavity
How We See • Light rays pass through: • Cornea • Pupil • Aqueous humor • Lens • Vitreous humor • Then strike retina • Stimulating rods and cones
Figure 13.6The path of light through the cornea, pupil, lens, and striking the retina.
How We See • Upside-down image forms on retina • Optic nerve transmits this image to brain • Brain turns upside-down image into right-side up image
Figure 13.7The image formed on the retina is inverted. The brain rights the image as part of the interpretation process.
Vision • Vision requires four mechanisms: • Coordination of external eye muscles so that both eyes move together • Correct amount of light admitted by pupil • Correct focus of light upon retina by lens • Optic nerve transmitting sensory images to brain
Additional Combining Forms • aden/o – gland • angi/o – vessel • bi/o – life • cry/o – cold • cyst/o – sac • esthes/o – sensation, feeling • myc/o – fungus • ton/o – tone • xer/o – dry
Additional Suffixes • -al pertaining to • -algia pain • -ar pertaining to • -ary pertaining to • -atic pertaining to • -ectomy surgical removal • -edema swelling • -graphy process of recording
Additional Suffixes • -ia condition • -ic pertaining to • -ism state of • -itis inflammation • -logist one who studies • -logy study of • -malacia softening • -meter instrument to measure
Additional Suffixes • -metry process of measuring • -oma tumor • -osis abnormal condition • -otomy cutting into • -ous pertaining to • -pathy disease • -pexy surgical fixation • -phobia fear