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Features of Middle Ear

For hearing- the external, middle and inner ear.
For equilibrium
- the semicircular canals (SC), the utricle and saccule of the inner ear
  1. Semicircular canals sense rotational acceleration
  2. The utricle senses linear (horizontal) acceleration
  3. The saccule senses linear (vertical) acceleration.

The receptors for both hearing as well as equilibrium are the hair cells. There are 6 groups of hair cells in each ear viz 3 in semicircular cells, 1 each in the utricles saccule and cochlea.



  1. Ext. auditory canal
  2. Tymp. Membrane
  3. Eustachean tube/ Auditory tube/ Pharyngotympanic tube
  4. Oval window
  5. Round window
  6. Reissner’s membrane
  7. Basilar membrane
  8. Organ of corti


  1. It is air- filled space in the temporal bone
  2. The auditory tube (also called eustachean tube, pharyngotympanic tube) connects the middle ear cavity (also called cavity) with the nasophanynx. The auditory tube in usually closed; it opens during swallowing, chewing, yawning. When the tube opens, there is equalization of pressures on the two sides of the tympanic membrane.
  3. There are 3 bones- malleus, incus and stapes.
  4. There are 2 muscles – tensor tympani and stapedius.
  5. The tympanic membrane functions as a resonator that reproduces the vibrations of the sound source. The motions of the tympanic membrane are imparted to the manubrium of malleus to the incus to the foot plate of the stapes at oval window. The auditory ossicles thus function as a lever system they increases the sound pressure that arrives at the oval window, because the lever action of the malleus and incus multiplies the force 1.3 times and the area of the tympanic membrane is much greater than the area of the foot plate of the stapes.This is called IMPEDENCE MATCHING

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