AnatomyOfTheEar - Anatomy of the Ear Ear has three regions...

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Anatomy of the Ear Ear has three regions outer middle inner outer and middle are concerned with the transmission of sound to the inner ear inner ear converts sound to fluid motion and then to electrical impulses (action potentials) The Physiology of the Ear Outer Ear Auricle (pinna)- flap of elastic cartilage External auditory canal Tympanic membrane (eardrum)- semitransparent thin fibroelastic connective tissue membrane, covered by epidermis on the external side and a simple low cuboidal mucous epithielium on the inner side External Auditory Canal Middle Ear Ossicle s (malleus, incus, stapes) Oval window Round window Opening into the Eustachian tube Inner Ear Vestibular apparatus for balance and equilibrium Cochlea for hearing Sound Results from the motion of air molecules which oscillate. Compression and rarefaction with ea. pressure pulse --> pressure waves. Sound waves travel in all directions from their source. Ears and Hearing Waves are characterized by frequency and intensity. Frequency: Measured in hertz (cycles per second). Greater the frequency the higher the pitch. Intensity: Directly related to amplitude of sound waves. Measured in decibels. Outer Ear The shape of the outer ear (auricle) increases the intensity of the intermediate frequencies: those that are most important for preception of speech sounds Sound waves are funneled by the auricle into the external auditory meatus.
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External auditory meatus channels sound waves to the tympanic membrane. Increases sound wave intensity. Middle Ear Bones The ossicles (the smallest bones in the bondy) amplify the sound 20 X due to leverage advantage: sensitivity to soft sounds -disadvantage; possible damage to sensory cells from loud sounds Middle Ear ( Cavity between tympanic membrane and cochlea) Malleus Attached to tympanic membrane. Vibrations of membrane are transmitted to the stapes. Incus : Anvil. Stapes : Attached to oval window. Vibrates in response to vibrations in tympanic membrane. Muscles of the Middle Ear Stapedius the smallest skeletal muscle in the human body. connects to the stapes (the stirrup) when it contracts, it reduces the action of the stapes (i.e., it reduces amplification) contracts just before speaking and chewing because our own speaking and chewing actually could be loud enough to damage the sensitive mechanisms of the inner ear if the sounds were further amplified. innervated by a branch of the Facial Nerve (CN VII). Muscles of the Middle Ear Tensor tympani inserts on the malleus and acts to tense the tympanic membrane reducing the effectiveness of sound transmission, protecting the inner ear during loud sounds. innervation from a branch of the mandibular nerve (V3 of CN V).
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This note was uploaded on 12/08/2011 for the course AMY 2A taught by Professor Jamesivey during the Spring '06 term at Riverside Community College.

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AnatomyOfTheEar - Anatomy of the Ear Ear has three regions...

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