The Ear Functions Basic Functional Unit The Ear • Detection of rotational movements • Detection of gravity • Detection of sound • Aide in speech • Recall: what is the function of cilia? • BFU of the ear = Hair Cell+ – Sorry, you do sound like your voice mail recording! Ossicles Pinna or Auricle Incus Malleus Stapes Semicircular Canals Tympanic External Membrane Auditory Meatus External Ear External Ear • Auricle or Pinna • Funnels, amplifies, and transmits sound waves – Directional sensitivity (cup your ears) • Made of skin & cartilage Middle Ear Cochlea Eustachian Tube The Ear • Sensory Organ • Hearing & Equilibrium • 3 sections – External – Middle – Inner Inner Ear External Ear • External Auditory Meatus (Canal) – ~2cm long “tube” – Encompassed by cartilage & bone – Lined with hair & glands (cerumen & sweat) • Antimicrobial, insect repellant Vestibulocochlear Nerve (CN8) Not always in balance! Ha-ha External Ear • Tympanic Membrane (eardrum) – Covers the proximal end of the canal – Made of layers of skin (fibrous tissue & mucus membrane) – Shiny, translucent, pearly Middle Ear • Eustachian Tubes – Connects throat with middle ear (1 continuous membrane) – Drains any fluid build up to throat • Infections can travel via tube… Inner Ear • Vestibule – Nerves leave this area to go to the brain • Semicircular canals – Balance & equilibrium – Hair-like receptors in fluid detect movement • Cochlea – Organ of Corti responsible for hearing – Hair-like receptors in fluid detect sound waves Middle Ear Structures that Equalize Pressure • Oval Window & Round Window • Eustachian Tube: equalizes pressure behind the tympanic membrane Middle Ear • Air-filled cavity in temporal bone – Detects vibrations, amplifies sound waves • 3 bones – auditory ossicles – Malleus (hammer) – Incus (anvil) – Stapes (stirrup) Inner Ear • Fluid filled chambers – Perilymph (between membranous & bony labyrinth) – Endolymph (within membranous labyrinth) • Activation of mechanoreceptors generates nervous impulses = hearing & equilibrium Hearing 1. Sound waves enter the outer ear & travel through the ear canal to the tympanic membrane Hearing Hearing 2. Tympanic membrane vibrates, passing those vibrations on to the ossicles in the middle ear 3. Ossicles amplify the sound vibrations & send them to the cochlea. The vibrations activate the tiny hair cells, which in turn release neurochemical messengers . Mechanism of Hearing Answers The___________ directs sound waves to the _________________, and sets the _________ membrane vibrating. This vibration passes through the _______, ________, and _________ bones. The footplate of the ________ moves backwards/forwards over the _______ window. This sets up fluid vibrations of the ________ within the cochlea. Vibrations of the basilar membrane stimulate the _____ cells of the organ of corti. An electrical impulse is than carried via the _______ nerve to the _____________ nerve and to the brain where interpretation occurs. Ear Conditions • Otitis Externa (“Swimmer’s Ear”) –Inflammation of the external auditory meatus –Common Causes • Bacterial infection • Fungal infection • Irritation or Allergies –Possible triggers: • Moisture, damage, chemicals, skin conditions… • • • • • • • • • • • • Hearing 4. The auditory nerve carries the signal to the brain, which translates it into a sound you can understand. Auricle External auditory canal Tympanic Malleus Incus Stapes Stapes Oval Endolymph Hair Cochlear Vestibulocochlear Ear Conditions • Otitis Media (Middle Ear Infection) –Caused by bacterial or viral infection –Common in young children due to immature anatomy Ear Conditions • Myringotomy – – tubes in the tympanic membrane to allow drainage of infection Ear Conditions • Hearing Loss –Commonly caused by: Overexposure to loud sounds Physical injury to the ear Infections Aging Ear Conditions Deafness • Conductive Deafness: interference with the transfer of vibrations – Many treatments – Limitations?