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Lecture #18 - The Ear.doc

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Anatomy and Cell Biology
ANAT 101
Richard Oko

Lecture #18 - The Ear and the Auditory and Vestibular Systems Regions of the Ear external/outer ear -> collects + directs sound waves middle ear -> amplifies sound waves internal/inner ear -> contains sensory organs for hearing and balance EXTERNAL EAR • directs waves towards tympanic membrane • lateral 1/3 of canal = cartilage • medial 2/3 = temporal bone THE MIDDLE EAR • air-filled bony compartment with several key features -3 bones (ossicles): vibrate to amplify sound waves -malleus, incus, stapes -2 muscles: control excessive vibration of ossicles -tensor tympani and stapedius -Eustachian tube: connects ear to nasopharynx -equalizes air pressure -drains mucus build up Otitis Media (middle ear infection) -earache, fever, hearing loss -caused by fluid buildup in tube -occurs more in children -have a shorter, more horizontal tube -can cause perforation of tympanic membrane THE INTERNAL EAR • 3 sensory organs -hearing -> cochlea Lecture #18 - The Ear and the Auditory and Vestibular Systems -balance/equilibrium -> semicircular canals, vestibule -openings (windows) to middle ear -> oval window, round window Cochlea -auditory system (hearing) -spiral shaped structure containing Organ of Corti (transduces sound waves into electrical impulses for brain) Vestibule -vestibular system (balance) - static equilibrium -located between cochlea and semicircular canals -made up of utricle and saccule -> detect gravity and linear acceleration Semicircular canals -vestibular system (balance) - dynamic equilibrium -3 canals (anterior, posterior, lateral) that detect complex rotational motion -bony labyrinth contains perilymph surrounding membranous labyrinth -membranous labyrinth contains endolymph filling the sensory structures AUDITORY SYSTEM and Cochlea • movement of stapes spread fluid waves through compartments of cochlea (from oval window to round window) 2 compartments (separated by cochlear duct) • 1) scala vestibuli 2) scala tympani Lecture #18 - The Ear and the Auditory and Vestibular Systems Organ of Corti (aka spiral organ in cochlear duct) -where sound transduction takes place through hair cells The Hair Cell • sensory receptor that transduces mechanical and electrochemical energy • stereocilia: fingerlike projections on apical surface of cell • activation of cell occurs mechanically by bending of stereocilia • activated hair cell releases NT, stimulates sensory neuron to brain Lecture #18 - The Ear and the Auditory and Vestibular
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