Human Ear Anatomy PDF

• 1. First hit outer part of ear, known as the pinna. 2. Then the sound gets funneled from the pinna to the auditory canal (also known as external auditory meatus). 3. Then from the auditory canal they hit the tympanic membrane (also called the eardrum). 4. As pressurized wave hits eardrum, it vibr...

• 1. First hit outer part of ear, known as the pinna. 2. Then the sound gets funneled from the pinna to the auditory canal (also known as external auditory meatus). 3. Then from the auditory canal they hit the tympanic membrane (also called the eardrum). 4. As pressurized wave hits eardrum, it vibrates back and forth, causing 3 bones to vibrate in this order: i. malleus (hammer) ii. incus (anvil) iii. stapes (stirrup) *[acronym: MIS] *Three smallest bones in the body. *These bones combined are also referred to as the ossicles. 5. Stapes is attached to oval window (aka elliptical window). The oval window then vibrates back and forth. 6. As it gets vibrated, it pushes fluid and causes it to go in/around cochlea (a round structure lined with hair cells). 7. At tip of cochlea (inner most part of circle), where can the fluid now go? It can only go back, but goes back to the round window (circular window) and pushes it out. 8. The reason doesn’t go back to oval window, is because in middle of cochlea is a membrane – the organ of Corti (includes the basilar membrane and the tectorial membrane). 9. As hair cells (cilia) move back and forth in the cochlea – electric impulse is transported by auditory nerve to the brain. o Place theory is a theory of hearing which states that our perception of sound depends on where each component frequency produces vibrations along the basilar membrane. By this theory, the pitch of a musical tone is determined by the places where the membrane vibrates, based on frequencies corresponding to the tonotopic organization of the primary auditory neurons. Place theory posits that one is able to hear different pitches because different sound waves trigger activity at different places along the cochlea’s basilar membrane. 10. The above process of fluid going around the cochlea keeps occurring till the energy of the sound wave dissipates and stops moving. Occurs more = more hair cells vibrate. General classification of the ear o External/Outer ear: from pinna to tympanic membrane o Middle ear: From malleus to stapes (three ossicles) o Inner ear: Cochlea and semicircular canals 28