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PowerPoint® Lecture Slide Presentation by Patty Bostwick-Taylor, Florence-Darlington Technical College Ears and Hearing 8 PART B Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear The ear is divided into three areas External (outer) ear Middle ear (tympanic cavity) Inner ear (bony labyrinth) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Ear Houses two senses Hearing Equilibrium (balance) Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear Figure 8.12 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The External Ear Involved in hearing only Structures of the external ear Auricle (pinna) Funnels sound waves External acoustic meatus (auditory canal) Narrow chamber in the temporal bone Lined with skin and ceruminous (wax) glands Ends at the tympanic membrane Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Why wax? The actual wax that is observed is the coating of the inside of your ear in order to protect it from things entering the ear canal. Ear wax is produced by a gland that is inside your ear, to help keep away dirt, bugs, and even germs. When your ears are not cleaned for a long time, the wax eventually just dries up and falls out in tiny, flaky bundles that you don't even realize. ~D.W. Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Middle Ear (Tympanic Cavity) Air-filled cavity within the temporal bone Only involved in the sense of hearing Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The Middle Ear (Tympanic Cavity) The opening from the auditory canal is covered by the tympanic membrane Tympanic Membrane - vibrates in response to pressure changes The auditory tube connects the middle ear with the throat Allows for equalizing pressure during yawning or swallowing Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear Figure 8.12 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings The auditory tube If pressure outside is greater than inside, ears will “pop” Chewing gum can help equalize pressure Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Ear Infections (Otitis media) Don’t close nostrils when blowing nose, can force debris into the ears causing infection of the middle ear (otitis media) Frequent ear infections can receive “tubes” for drainage Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Bones of the Middle Ear (Tympanic Cavity) Three bones (ossicles) span the cavity Malleus (hammer) Incus (anvil) Stapes (stirrip) Function Vibrations from eardrum move the Malleus Incus Stapes inner ear Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear Figure 8.12 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Inner Ear or Bony Labyrinth Vibrations enter through the oval window from the Stapes Vibrations move perilymph fluid in: Semicircular canals Sensing equilibrium Vestibule Connects semicircular canals to cochlea Cochlea Contains the hairs for hearing senses Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Cochlea Hair Cells Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings A sense of hearing Cell membrane protein channels open in response to changes in frequencies Allow Ca+2 ions to flow into the cells Triggers neurotransmitter release Sends signal through vestibulocochlear nerve to the brain Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Anatomy of the Ear Figure 8.12 Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Decibels (dB) - measure sound intensity 0 dB - least perceptible by humans 40 dB - whispering 60-70 dB - normal conversation 80 dB - heavy traffic 90 dB - above this can damage hearing receptors 120 dB - Rock concert 140 dB - Jet plane takeoff Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings Partial or complete hearing loss Eardrum can harden as a result of disease Eardrum can tear or perforate due to disease or injury Loud sounds, tumors, brain damage or drug use can damage nerve pathways Copyright © 2009 Pearson Education, Inc., publishing as Benjamin Cummings