Select the true statements about ossicles:
Select all correct answers.
a) When the tensor tympani muscle and stapedius muscles contract, sounds are amplified to the inner ear.
b) When the tensor tympani muscle and stapedius muscles contract, sounds are attentuated to the inner ear.
c) The stapes creates increased pressure on the smaller oval window to amplify sound.
d) The stapes creates decreased pressure on the smaller oval window to amplify sound.
e) The stapes creates increased pressure on the smaller tympanic membrane to amplify sound.
f) The stapes creates decreased pressure on the tympanic membrane to amplify sound.
The correct answer and explanation is:
The correct answers are:
- b) When the tensor tympani muscle and stapedius muscles contract, sounds are attenuated to the inner ear.
- c) The stapes creates increased pressure on the smaller oval window to amplify sound.
Explanation:
The ossicles are three tiny bones in the middle ear that play a crucial role in transmitting sound vibrations from the eardrum (tympanic membrane) to the inner ear. These bones include the malleus, incus, and stapes. They work together to amplify sound and transfer it efficiently to the inner ear.
- Tensor tympani and stapedius muscles: These muscles contract in response to loud sounds in a protective mechanism known as the “acoustic reflex.” The contraction of these muscles reduces the vibrations of the ossicles and attenuates the sound that reaches the inner ear, helping to protect the inner ear from excessive sound levels. Therefore, statement b is correct. When these muscles contract, the sound is indeed attenuated, not amplified.
- The stapes and the oval window: The stapes is the last bone in the ossicular chain, and it connects to the oval window of the cochlea in the inner ear. When the stapes vibrates, it pushes on the oval window, which is smaller than the tympanic membrane. This action increases the pressure on the fluid inside the cochlea and amplifies the sound. Statement c is correct because the stapes does indeed increase pressure on the oval window to amplify sound.
Incorrect Answers:
- a) When the tensor tympani muscle and stapedius muscles contract, sounds are amplified to the inner ear. This is incorrect because the contraction of these muscles actually dampens sound to protect the inner ear, not amplify it.
- d) The stapes creates decreased pressure on the smaller oval window to amplify sound. This is incorrect because the stapes increases pressure on the oval window to amplify the sound.
- e) The stapes creates increased pressure on the smaller tympanic membrane to amplify sound. The tympanic membrane is not where the amplification occurs. The stapes acts on the oval window, not the tympanic membrane.
- f) The stapes creates decreased pressure on the tympanic membrane to amplify sound. Again, this is incorrect because the stapes does not act directly on the tympanic membrane.
In summary, the ossicles and their associated muscles help ensure that sound is effectively transmitted and protected in the ear.