加拿大高三生物耳朵.pptVIP

The Outer Ear The PINNA is the outer part of the ear that can be seen acts like a funnel for sound channeling the sound from a large area to a small area the AUDITORY CANAL carries sound waves to the eardrum contains specialized sweat glands which produce EARWAX thick substance that traps foreign particles and prevents them from entering the ear The Middle Ear The TYMPANIC MEMBRANE (a.k.a. eardrum) marks the beginning of the middle ear flexible membrane that responds to compressions sound vibrations strike the eardrum and cause it to vibrate at the same frequency and amplitude as the vibrations Bones called OSSICLES carry the sound waves to the inner ear where they are eventually converted to an electrical impulse and transmitted to the brain the ossicles are: 1. MALLEUS (HAMMER) struck by the vibrating eardrum (magnifies force 20X) 2. INCUS (ANVIL) between the malleus and the stapes 3. STAPES (STIRRUP) strikes the membrane which covers the oval window in the inner ear vibrations from the sound waves travel through the ear as follows: tympanic membrane ?malleus ?incus ? stapes ?oval window The Eustachian Tube tube about 40 mm x 3 mm which connects chamber of throat/nose and the middle ear equalizes pressure between the middle and outer ear when you increase altitude you decrease air pressure the pressure in the middle ear becomes greater than the outer ear and the eardrum is pressed outwards (ouch!) the Eustachian tube opens to equalize pressure between the throat and middle ear because the throat would have the same pressure as the air The Inner Ear and Hearing The inner ear is full of fluid which transmits sound through the cochlea the COCHLEA is the snail-shaped structure that converts mechanical vibrations into electrical messages which are sent to the brain the cochlea consists of 3 coiled chambers: 1. VESTIBULAR CANAL sound waves first enter here from the OVAL WINDOW and travel down towards the tympanic canal which is connected TYMPANIC CANAL sound wav