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66 Cards in this Set
- Front
- Back
acoustic energy |
outer ear |
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mechanical energy |
middle ear |
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fluid energy |
middle ear
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temporal bone |
contains the sensory organs of hearing, balance and the human ear |
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outer ear anatomy |
auricle/pinna ear canal/external auditory meatus outer layer of ear drum (tympanic membrane) |
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auricle/pinna |
skin covered cartilage of outer ear, no fatty layer underneath |
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helix of pinna |
upper rim |
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lobule of pinna |
ear lobe |
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concha |
bowl of pinna at entrance of ear canal |
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osseocartilaginous junction |
connection between cartilaginous portion and bony portion of external auditory meatus |
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first 1/3 of EAM |
skin covered cartilage |
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inner 2/3 of EAM |
skin covered bown
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size of EAM |
2.3-2.9 cm in length, .7 cm in diameter |
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EAM shape |
has a downward bend at the auricle to protect the eardrum from outside substances |
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diameter of TM |
.9cm, slightly larger than EAM because of a 55 degree angle |
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shape of TM |
concave and slightly inward like a cone shape |
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pars flaccida |
superior portion, 1/10 of TM more flexible portion/less strong does not have a middle fibrous layer does not participate largely in transduction of acoustic signal |
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pars tensa |
9/10 of TM very strong, made of tightly woven fibers to protect ear drum |
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annulus |
thickened fibrocartilagenous ring fixed to tympanic bone surrounding membrane 3/4 of the way around it |
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otoscopic evaluation |
a cone of light is present that reflects of the malleus (umbo) in the tympanic membrane |
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two parts of malleus that connect to the TM |
umbo (lower part) manubrium of malleus (more central part) |
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part of incus attached to TM |
long arm of incus |
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outer ear physiology |
collect and resonate sound assist in sound localization protect the middle ear |
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resonant freq of ear canal |
2700 Hz |
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resonant freq of pinna+ concha together |
5000 Hz (high freq) |
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total enhancement of resonant freqs of outer ear |
+20 db around 3500 Hz |
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head related transfer function |
-the way sounds bounce off diff parts of body may contribute to sound localization (diffraction and reflection properties of head, pinna torso before reaching ear) -use timbre differences from sounds coming from diff directions -sounds will lose some freq when they hit body parts |
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interaural time difference (ITD) |
calculate the difference in time each ear hears the sound to determine where its coming from -best for lower freq sounds because they can bend and won't lose intensity (will arrive at opposite ear at same intensity but diff time) |
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interaural intensity difference (IID) |
calculate the difference of intensity of the sound at each ear to determine where the sound came from -best for higher freq sounds because they can't bend when presented with an obstacle and will lose intensity when it reaches the farther ear (inverse square law) |
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cerumen |
sebaceous glands in ear canal secrete cerumen -protects skin/prevents foreign objects from entering ear canal -antibacterial/antifungal properties |
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cilia |
hairs in outer 1/3 of ear canal point outward toward the pinna
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middle ear anatomy |
-middle/inner layers of tympanic membrane -ossicles/middle ear bones (malleus, stapes, incus) -eustachian tube -ligaments/muscles -oval/round windows |
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three layers of TM |
-outer epithelial layer -inner mucosal layer -middle fibrous layer |
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outer epithelial layer of TM |
continuous with skin lining of ear canal |
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inner mucosal layer of TM |
continuous with mucous of middle ear |
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middle fibrous layer of TM |
encloses handle of malleus has 3 types of fibers-radial, circular and parabolic |
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tympanic membrane physiology |
separates outer ear from middle ear -transmits acoustic sounds from air to ossicles by vibrating (mechanical) -malleus is connected to ear drum at the umbo and short arm of the malleus |
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two parts of middle ear cavity |
-tympanic cavity -attic/epitympanic recess |
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tympanic cavity |
opposite tympanic membrane (part of middle ear cavity) |
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epitympanic recess/attic |
above the level of the tympanic membrane contains upper half of malleus and greater part of incus |
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middle ear cavity characteristics |
-irregular shape -filled with air (from nasopharynx through eustachian tube) -houses the ossicular chain (connected from lateral wall/malleus to medial wall/stapes) |
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tegmental wall of middle cavity |
"roof" formed by a thin plate of bone ceiling of epitympanic recess (upper part of malleus/incus) |
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jugular wall of middle cavity |
"floor" separates tympanic cavity from the jugular fossa |
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medial wall |
-opening to the cochlea -fenestrae vestibuli (oval window) and rotunda (round window) -promontory of the cochlea (between the windows) and the facial nerve VII |
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anterior wall (towards front of face) |
tendon of the tensor tympani muscle (connected to malleus) -opening to the auditory tube/eustachian tube |
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posterior wall (towards back of head) |
attachment of stapedius muscle (connected to stapes) -access to mastoid bone air cells through aditus and antrum |
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lateral wall (closest to outer ear) |
contains tympanic membrane |
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ossicles |
3 smallest bones in the body (malleus incus stapes) -connect TM on lateral wall to oval window of the cochlea on medial wall -have true articular joints |
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malleus |
manubrium and short process (umbo) connected to TM -attached to lateral wall by lateral ligament -head of the manubrium is attached to the body of the incus |
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incus |
attached to posterior wall via superior ligament -long process is attached to head of stapes |
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stapes |
sealed to the entrance of the cochlea/inner ear by annular ligament + footplate |
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eustachian tube |
connects middle ear to nasopharynx -equalizes pressure(pressure changes of middle ear impact TM) -drains fluid -normally closed, opens during swallowing/yawning -beings in anterior wall 36mm in length |
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eustachian tube in children |
it is more horizontal in infancy children unable to drain fluid as easily -common for children to have fluid in ears secondary to ear infections |
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acoustic reflex |
middle ear muscles that contract in response to a loud sound |
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stapedius muscle |
attached from posterior wall to stapes -primary muscle of acoustic reflex, only one measured in audiology -contracts pulling stapes backwards(towards TM) -decreases movement of stapes, dampens hearing sensitivity |
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tensor tympani |
attached from anterior wall to malleus -contracts pulling TM inward in response to internal sounds (chewing) and non auditory stimuli (puff of air to the eye) -TM stiffens, doesnt vibrate as easily, dampens hearing sensitivity |
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physiology of the middle ear |
1. three impedence matching mechanisms 2. pressure equalizer 3. protection
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impedance matching device |
middle ear carries mechanical energy from TM to fluid filled inner ear (change of resistance from air-fluid) -if sound pressure waves were applied directly to inner ear 99.9% of acoustic energy because of fluid -even with ossicles there is a loss of 33dB -middle ear has to account for this |
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middle ear increases pressure to match impedence by |
1. increasing force 2. decreasing area 3. both 1 and 2 at the same time |
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middle ear impedence matching mechanism TM to footplate (area ratio) |
-area of the TM is 17x greater than the footplate of the stapes -decrease in size from TM to the footplate without change in force results in a 17x increase in pressure (+25dB)
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middle ear impedence matching mechanism malleus to incus (lever action) |
-length of manubrium of malleus is 1.3x length of incus -pivot point (connection) of malleus/incus is closer to incus and therefore the malleus uses less force to move it (like a seesaw) -results in an increase in pressure on the incus (+2dB) because of force applied to a smaller incus, therefore applied to oval window |
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middle ear impedence matching mechanism TM shape (buckling) |
-flexible/cone shaped TM curves from its rim at both ends to its attachment at the umbo -results in greater movement/displacement of the TM and not the malleus manubrium/ umbo (higher pressure) -product of force/displacement must be equal on both sides of TM -+6dB gain |
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total gain from middle ear impedance matching |
33 dB (25dB+2dB+6dB) -about as much that would be lost by converting from mechanical energy (middle ear) to hydraulic energy (inner ear) |
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middle ear transfer function |
doesn't transmit all freqs equally, better sensitivity to mid freq range (900-5kHz) -gain of pressure/dB depends on freq, resonancy characteristics, and phase diff between pressure wave at oval window and phase at TM |
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pressure equalizer |
eustachian tube equalizes pressure between middle ear cavity and external auditory meatus by opening and letting in air from nasopharynx -if unable to open, negative pressure in ME can suck in TM and make it stiff/resistant to vibration |
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contraction of auditory reflex |
bilateral contraction of middle ear muscles (tensor tympani and stapedius) primarily stapedius -contraction increases w increased intensity (AR growth) to a point (plateau) -85 dB causes the contraction in both ears even if loud sound is only presented to one ear -dampens sounds by stiffening ossicle chain (low freqs) |