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Anatomy Physiology and Disorders of the Hearing Major Divisions of the Ear Peripheral Mechanism VIII Outer Middle Inner Cranial Ear Ear Ear Nerve Central Mechanism Brain Question What is the purpose of the pinna? A. Cosmetics B. Sound collector C. Same side localization D. A and B E. B and C Outer/External Ear Pinna External Auditory Meatus • Auricle=Pinna • Cerumen=Wax • External Auditory Meatus= Hole in temporal bone (leads to Auditory canal) • Tympanic Membraneear drum Pinna Question Another name for pinna? A. External auditory meatus B. External auditory canal C. Ear lobe D. Auricle E. None of the above Function of Outer Ear • • • • • Collect sound Localization Resonator Protection Sensitive (earlobe) • Other? Pinna • localizes • Directs sound into the ear • Each individual's pinna creates a distinctive imprint on the acoustic wave traveling into the auditory canal Question Cerumen should be routinely removed from the ear canal? A. True B. False Cerumen • Repel water • Trap dust, sand particles, microorganisms, and other debris • Moisturize epithelium in ear canal • Odor discourages insects • Antibiotic, antiviral, antifungal properties – Cleanse ear canal Tympanic Membrane • Separates outer from the middle ear • Protective barrier to the middle ear • Cone-shaped (depressed inward) • 1st to vibrate in response to sound waves. External Ear Care Hazardous to health: • Ear candling • Swabs • Foreign objects Outer Ear Hearing Disorders • Outer ear • CHARGE • Down Syndrome – Ears small and low set • Fetal Alcohol Syndrome – Deformed ears Grow Ear? The big picture • Size and shape What is sound? • Sound is a form of energy that can be heard and travels in waves. • When matter vibrates or moves back and forth very quickly, a sound is made. • Sound waves can travel through solids, liquids, or gases. • Sound makes the air vibrate. • For sound to be heard, sound vibrations must have air or some other kind of matter to travel through. • Can’t hear sound in outer space because there is no air or other matter to carry sound vibrations. Middle Ear The function of the middle ear is to? A. Cause middle ear infections in young children B. Amplify sounds C. Interpret sounds D. Analyze sounds E. None of the above Middle Ear What are the parts of the middle ear? A. Ossicles and cochlea B. Ossicles and eustachian tube C.Tympanic membrane and auricle D.I don’t know Middle Ear Ossicles Middle Ear Muscles Eustachian Tube Mastoid Function of Middle Ear • Conduction – Conduct sound from the outer ear to the inner ear • Protection – Creates a barrier • Transducer – Converts sound waves to mechanical energy • Amplifier Middle Ear (parts) • Auditory Ossicles malleus, incus, stapes transmit vibrations and amplify the signal • Eustachian tubeconnects the middle ear to the throat - helps maintain air pressure Eustachian Tube • Connects the middle ear with the nasopharynx • Opens during swallowing and yawning • This equalizes the pressure on either side of the eardrum • Necessary for optimal hearing. – Without this function the eardrum could prolapse. – Plugged ears on a plane The Eustachian tube: A. Opens when one yawns B. Opens when one smiles C. Opens when one blinks D. It is always open E. Never opens Ossicles • Malleus (hammer) • Incus (anvil) • Stapes (stirrup) smallest bone of the body Middle Ear Disorders • Middle Ear disorders – Acute otitis media – TM Perforation Question The function of the inner ear: A. Balance B. Hearing C. Touch D. All the above E. A and B Inner Ear = Labyrinth • Labyrinth series of fluid filled tubes responsible for equillibrium (balance) and hearing. • Made of 2 main regions: Semicircular canals & Cochlea • Semicircular Canals - sense of equilibrium • Cochlea – senses hearing • Organ of Corti - contains hearing receptors, hair cells detect vibrations Organ of Corti Inner Ear: Cochlea • Inside the cochlea are special neurons called HAIR CELLS • The stapes is attached to the OVAL WINDOW, and vibrations cause the fluid in the inner ear to vibrate • This moves the hair cells, transmitting the vibration. • Therefore the HAIR CELLS in this region are receptors for HEARING. Sense of Equilibrium • Static Equilibrium - sense the position of the head, maintain stability and posture • Dynamic Equilibrium (semicircular canals) balance the head during sudden movement • Cerebellum (brain)interprets impulses from the semicircular canals and maintains overall balance and stability Steps in Hearing 1. Sound waves enter external auditory meatus 2. Eardrum vibrates 3. Auditory ossicles (malleus, incus, stapes) amplify vibrations 4. Stapes hits oval window and transmits vibrations to cochlea 5. Organs of corti contain receptor cells (hair cells) that deform from vibrations 6. Impulses sent to the vestibulocochlear nerve 7. Auditory cortex of the temporal lobe interprets sensory impulses 8. Round window dissipates vibrations within the cochlea
