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Anatomy and Physiology of the Ear Eslam Osman, M.D.,F.R.C.S (ORL, H&N Surgery) 02/07/08 Tinnitus Support Group 1 Divisions Of The Ear External Ear Middle Ear Inner Ear Central Auditory Nervous System 02/07/08 Tinnitus Support Group 2 02/07/08 Tinnitus Support Group 3 Structures of the Outer Ear Pinna Collect sound Localization Resonator Protection 02/07/08 Tinnitus Support Group 4 External Auditory Canal Extends from the pinna to the tympanic membrane 1 1/2 inch in length Protects the eardrum Wax 02/07/08 Tinnitus Support Group 5 Structures of the Middle Ear Tympanic Membrane Tympanic Cavity Ossicles Middle Ear Muscles Eustachian Tube Mastoid 02/07/08 Tinnitus Support Group 6 Tympanic Membrane The eardrum separates the outer ear from the middle ear Creates a barrier that protects the middle and inner areas from foreign objects The eardrum vibrates in response to sound pressure waves. Changes acoustic energy into mechanical energy 02/07/08 Tinnitus Support Group 7 Ossicles Malleus (hammer) Incus (anvil) Stapes (stirrup) smallest bone of the body 02/07/08 Tinnitus Support Group 8 Middle Ear Muscles Tensor tympani • Attached to malleus Stapedius • Attached to stape Middle Ear Muscle Function: • • • 02/07/08 Help maintain ossicles in proper position Protect inner ear from excessive sound levels This protective reflex termed "acoustic reflex" Tinnitus Support Group 9 Eustachian Tube The ET connects the front wall of the middle ear with the nasopharynx It operates like a valve, which opens during swallowing and yawning It equalizes the pressure on either side of the eardrum, which is necessary for optimal hearing. 02/07/08 Tinnitus Support Group 10 Mastoid Bony ridge behind the auricle Connect with middle ear Can get infected ( Mastoiditis) 02/07/08 Tinnitus Support Group 11 Function of Middle Ear Conduction Protection Transducer Amplifier 02/07/08 Tinnitus Support Group 12 Amplifier The middle ear enhances the transfer of acoustical energy in two ways: • The area of the eardrum is about 17 times larger than the oval window The effective pressure (force per unit area) is increased by this amount. • The ossicles produce a lever action that further amplifies the pressure 02/07/08 Tinnitus Support Group 13 Structures of the Inner Ear Cochlea Vestibule Semicircular canals 02/07/08 Tinnitus Support Group 14 Cochlea Snail-shaped organ with a series of fluid-filled tunnels converts mechanical energy into electrical energy It contain Organ of Corti ( end organ of hearing) 02/07/08 Tinnitus Support Group 15 Traveling Waves 02/07/08 Tinnitus Support Group 16 Vestibular System Consists of vestibule and three semicircular canals Shares fluid with the cochlea Controls balance No part in hearing process 02/07/08 Tinnitus Support Group 17 Central Auditory Pathway Pathway between cochlea and auditory cortex Cochlear nerve Cochlear nucleus 02/07/08 Tinnitus Support Group 18 Causes of Tinnitus Local causes Every ear disease can be associated with deafness General Causes Cardiovascular disease Neurological conditions 02/07/08 Tinnitus Support Group 19 Classification of Tinnitus Unilateral or bilateral Subjective or objective Pulsatile or non pulsatile 02/07/08 Tinnitus Support Group 20 Key Points in History Accompanying ear disease History of noise exposure Trauma Ototoxic medications Systemic Diseases 02/07/08 Tinnitus Support Group 21 THANK YOU 02/07/08 Tinnitus Support Group 22