Stapedius

Stapedius is the smallest skeletal muscle in the human body. At just over one millimeter in length, it is located in the middle ear and controls the movement of the stapes, one of the three ossicles in the ear. The stapedius helps to dampen large vibrations of the stapes due to loud noise, protecting the inner ear from potential damage.

Anatomy

The stapedius muscle originates from the posterior wall of the tympanic cavity, and inserts into the neck of the stapes. It is innervated by the facial nerve (cranial nerve VII), which also controls all other muscles of facial expression.

Function

The primary function of the stapedius is to stabilize the stapes and prevent its excessive oscillation. It does this by contracting in response to high-intensity sound stimuli, thereby reducing the amount of movement and the subsequent vibration of the oval window. This is known as the acoustic reflex or stapedius reflex.

Clinical significance

Damage to the stapedius muscle or its nerve supply can result in hyperacusis, a condition characterized by an increased sensitivity to normal environmental sounds. This can be caused by a number of factors, including Bell's palsy, physical trauma, or surgical procedures involving the ear.

See also

• Tensor tympani
• Ossicles
• Middle ear
• Acoustic reflex

References

Stapedius Resources
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