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2_The Human Ear
- The Middle Ear
- Eustachian Tube: 1 ¾ inch-long tube that connects the middle ear with the back of the nasal cavity;
normally closed except when swallowing or yawning. Its function is that it equalizes air pressure insde
and outside the tympanic membrance and allows the drainage of normal and diseased middle ear
secretions.
- Ossicles; Function of Auditory ossicles: form the mechanical links between the tympanic membrane
and the inner ear; deliver sound vibration to inner ear fluids; amplify airborne sound by
approximately 30dB.
- Malleus: a small bone (hammer shaped); its handle attaches to the tympanic membrane at a place
called the umbo. Its other end has a round head.
- Incus: a small bone (anvil shaped) in which the malleus rests and then connects to the stapes.
- Stapes: a small bone (stirrup-shaped) which is connected to the incus, and with its oval footplate
connects to the oval window of the ear.
- Malleus: a small bone (hammer shaped); its handle attaches to the tympanic membrane at a place
called the umbo. Its other end has a round head.
- stapedius muscle
- tensor tympani muscle
- Oval window: is a membrane that connects the middle ear with the upper half of the cochlea. Its
function is that vibrations from the ossicles are transferred to the cochlea via the action of the stapedial
footplate in the oval window.
- Round window: membrane that connects the middle ear with the lower half oof the cochlea;
simultaneous outward motion of the round window called the round window reflex. Its function is the
aid in fluid motion within the cochlea and serves to equalize the hydraulic pressure.
- Eustachian Tube: 1 ¾ inch-long tube that connects the middle ear with the back of the nasal cavity;
normally closed except when swallowing or yawning. Its function is that it equalizes air pressure insde
and outside the tympanic membrance and allows the drainage of normal and diseased middle ear
secretions.
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