Anatomy of the Ear Chapter 8 Functions • Hearing • Equilibrium and Balance External Ear • Pinna (auricle) – Collects & directs sound waves into the auditory canal • External Auditory Canal – Short, narrow chamber that directs sound waves to the tympanic membrane • Tympanic membrane (eardrum) – Sound waves vibrate the membrane Middle Ear (tympanic cavity) • Air filled cavity • Auditory (Eustachian) tube – Connects middle ear to throat – helps equalize pressure in ear Did you know… In infants, the auditory tube is more horizontal, therefore, when children get sore throats they usually are more prone to ear infections. • Spanned by ossicles which transmit the vibratory motion of the eardrum to the oval window and the fluids of the inner ear – Malleus (hammer) – Incus (anvil) – Stapes (stirrup) Inner Ear • Osseous- bony chambers filled with fluid – Cochlea • Contains organ of Corti which contains hair cells (hearing receptors) that transmits the impulses to the vestibulocochlear nerve and finally the temporal lobe of the brain – Vestibule – Semicircular canals Hearing Sequence of Events 1. Pinna 2. External auditory tube 3. Tympanic membrane 4. Malleus 5. Incus 6. Stapes 7. Oval window 8. Organ of Corti in Cochlea 9. Hairs cells 10. vestibulocochlear nerve Equilibrium • Static (at rest) – Maculae (receptors) in vestibule report the position of the head to the pull of gravity when the body is not moving – Maculae transmit message to vestibular nerve that tells cerebellum your head’s position in space (balance) • Dynamic – Dynamic equilibrium receptors in semicircular canal respond to angular or rotatory movements of the head and transmit message to cerebellum via the vestibular nerve Deafness • Hearing loss of any degree • 2 kinds: – Conduction deafness • Something interferes with the conduction of sound vibrations to the fluids of the inner ear – Caused by: » Mechanical factors such as build up of earwax, fusion of ossicles, ruptured ear drum • Sensorineural deafness – Degeneration or damage to the receptor cells in the organ of Corti, the cochlear nerve or to neurons in the auditory cortex of the brain – Due to problem of nervous system structures Did you know…. Hearing Aids only improve the hearing of patients with conduction deafness.