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Definitions Pinna— Elastic cartilage
Tympanic membrane— eardrum
Ear ossicles— malleous, incus, stapes
Two membranes in inner ear— oval window, round window
Eustachian tube— connects ear to throatFunction— equalize pressure
Inner Ear Labyrinth Bony
Cochlea: Hearing Vestibule: Balance Semicircular canals:
Balance Membranous
Lymphs Endolymph
In membranous labyrinth
Perilymph Space between
membranous and bony labyrinth
Hearing Process
Waves move perilymph Perilymph moves vestibular membrane
that moves endolymph Endolymph moves tectorial membrane
which moves the hair cells Hair cells send impulse to nerves & the
brain Sound waves leave through round
window
Auditory Function
Vibrations produce sound waves Volume or loudness : number of hairs
stimulated Pitch: Function of wave frequency
Balance
Static Evaluates position
of head relative to gravity
Detects linear acceleration and deceleration
Kinetic Evaluates
movements of head 3 semicircular
canals Ampulla
endolymph moves when head moves
Ear Disorders Tinnitus
Ringing, clicking, whistling in ear due to disorders in middle or inner ear
Motion sickness Dysfunctions caused by stimulation of semicircular
canals during motion
Otitis Media Infections in the middle ear
Earache Results from otitis media, dental abscesses, TMJ
pain
Structure of the Eye Layers and coats Fibrous Tunic: Outer
Sclera—tough, white, outer portion; maintains shape,protects internal structures, provides muscle
attachment point; continuous with cornea
Cornea—transparent portion of anterior eye; avascular; bends & refracts light
Vascular Tunic: MiddleChoroid—middle layer; blood vessels & darkly
pigmented Ciliary body—holds ciliary muscles (smooth) attached to
lens w/ suspensory ligaments to control lens shape Lens- transparent; bioconvex
Iris—colored, smooth muscle ring with the pupil in the middle; controls light entering pupil
Structure of the Eye Continued
Retina—Inner Retina-incomplete,
innermost layer; nervous layer (contains neurons sensitive to light) Rods (black & white) Cones (color) Fovea Centralis/Macula
lutea- where light is focused; see fine images (area of greatest acuity)
Optic disc (no photoreceptor cells) AKA Blind Spot
Cavities (compartments) in the Eye
Anterior cavity—between the lens and cornea Filled with aqueous humor—clear, watery fluid Helps maintain intraocular pressure Glaucoma—too much intraocular pressure due to
too much aqueous humor
Posterior cavity—behind the lens and posterior portion of the eye Filled with vitreous humor—soft, gelatin-like
substance Helps with intraocular pressure to prevent collapse
Muscles of the Eye
Extrinsic eye muscle—skeletal muscles that move the eyeball
Intrinsic eye muscle—smooth muscles in the eye—involuntary Iris Ciliary body
Accessory structures
Eyebrows & eyelashes—keep some foreign particles out of eye
Eyelids—help with lubricationConjunctiva-mucus membrane lining the lid
(AKA Pink eye (conjunctivitis); caused by an infection or irritation
Closes from outside to in/ top to bottom
Lacrimal Apparatus Lacrimal apparatus
Lacrimal Gland: Produces tears to moisten, lubricate, wash
Lacrimal Canaliculi Collects excess tears
Punctum
Lacrimal Sac
Nasolacrimal duct Opens into nasal cavity
Concept Review
1. What are the 3 main layers of the eye?-sclera, choroid, retina
2. What are the 3 accessory structures and describe their function?
-eyebrows, eyelashes, & eyelids (protection & lubrication)
3. Where are tears formed and where do they go?
-lacrimal gland, nasalacrimal duct
How we see (4 main steps)Formation of Vision on the Retina
1. Refraction of light rays cornea, aqueous humor, lens, vitreous humor
2. Accommodation of lens Increase in curvature to achieve greater refraction
on near objects Emmetropia: Normal resting condition of lens Far vision: 20 feet or more from eye Near Vision: Closer than 20 feet
3. Constriction of pupil Iris contracts to limit the amount of light that
enters the eye
How we see Continued…Formation of Vision on the Retina
4. Convergence of eyesLight must hit the same spot of the retina
on both eyes to see only one objectBoth eyes are directed on the object at the
same angle
Single binocular vision —seeing one object with two eyes
Eye Disorders Myopia: Nearsightedness
Focal point too near lens, image focused in front of retina
Hyperopia: Farsightedness Image focused behind
retina
Presbyopia Degeneration of
accommodation, corrected by reading glasses
Astigmatism: Cornea or lens not uniformly curved
Strabismus: Lack of parallelism of light paths through eyes
Retinal detachment Can result in complete
blindness
Glaucoma Increased intraocular
pressure by aqueous humor buildup
Cataract Clouding of lens
Macular degeneration Common in older people,
loss in acute vision
Diabetes Dysfunction of peripheral
circulation
Structure of a Taste Bud
Gustatory cell—contain tiny, cilia-like gustatory hairs
Taste pore—opening in the papillae that is bathed in saliva
*The chemicals of food must dissolve in the saliva to stimulate the hairs to start an impulse.*
Sense of Smell
Olfactory organs Sensory hairs Olfactory cells Olfactory nerves Olfactory bulb Olfactory tract
Smelling
Substance must be:Able to become a gasWater soluble or very smallLipid soluble (to get into membrane)