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The Outer Ear Consists of:
• The Pinna - cartilaginous, highly variable in appearance, some landmarks.
• External Auditory Canal (or external auditory meatus) - 2.5 cm tube.
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Pinna Landmarks
• Helix• Antihelix• Concha• Tragus• Intertragal Notch• Antitragus
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External Auditory Canal
• lateral portion-cartilage• medial portion-osseous• lined with epidermal (skin)
tissue• hairs in lateral part• cerumen (ear wax)
secreted in lateral part.
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Outer Ear Functions
• Amplification / Filtering• Protection • Localization
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The Middle
Ear:A cleft within the temporal
bone
• Lining is mucous membrane• Tympanic Membrane separates it from EAC• Eustachian tube connects it to nasopharynx• Also Connected to Mastoid Air Cells 6
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Middle Ear Structures
1- Malleus2- Incus --Ossicles3- Stapes 4- Tympanic Membrane
(Eardrum)5- Round Window6- Eustachian Tube
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Middle Ear Muscles
1. The Stapedius Attaches to Stapes,Contracts in Response to Loud sounds, chewing, speaking; Facial (VIIth cranial) nerve
2. The Tensor Tympani Helps open Eustachian tube
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Middle Ear Functions
• Impedance Matching
• Filtering
• Acoustic Reflex
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Two Halves:• Vestibular--transduces motion and pull of gravity• Cochlear--transduces sound energy
(Both use Hair Cells)
INNER EAR
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The Stereocilia on IHCs and OHCs
• OHCs (at top)• V or W shaped ranks
• IHC (at bottom)• straight line ranks
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Cochlear Functions
• Transduction- Converting acoustical-mechanical energy into electro-chemical energy.
• Frequency Analysis-Breaking sound up into its component frequencies– Bekesy’s Traveling Wave– Active Tuning from OHCs
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Major Components of the Central Auditory Nervous System (CANS)
• VIIIth cranial nerve• Cochlear Nucleus• Superior Olivary Complex• Lateral Lemniscus• Inferior Colliculus• Medial Geniculate Body• Primary Auditory Cortex
Brainstem
Thalamus
Mid-brain
Temporal Lobe
<Trapezoid Body>
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Mid-Saggital View of Brain
Pons
Cerebellum
4th Ventricle
Thalamus
Corpus Callosum
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Cortical Processing
• Pattern Recognition
• Duration Discrimination
• Localization of Sounds
• Selective Attention
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Cerebral Dominance/Laterality
• Language Processing in the left hemisphere.(Remember the right ear has the strongest
connections to the left hemisphere)
• Most people show a right-ear advantage in processing linguistic stimuli
