Stapedius muscle

Stapedius muscle
origin
Eminentia pyramidalis
approach
Stirrup neck
function
tightens the annular ligament
Innervation
Stapedius nerve (branch of the facial nerve )

The stapedius muscle ( lat. For "stapes muscle ") belongs together with the tensor tympani muscle to the two internal muscles of the middle ear . The stapedius muscle uses a reflex arc, the stapedius reflex , to reduce the stapes' ability to vibrate and thus protects the inner ear from high sound levels.

Middle ear with tendon of the stapedius muscle and stapes head (framed in red)

The muscle has its origin within the Eminentia pyramidalis (Latin for pyramidal projection) in the sinus tympani (Latin for bay of the tympanic cavity). Its tendon leaves the eminentia pyramidalis through a small opening and pulls forward to the stapes neck, where it attaches. The innervation is provided by the stapedius nerve .

The stapedius muscle tilts the footplate of the stapes in the fenestra ovalis (Latin for oval window) and thereby tensions the annular ligament (Latin for ring-shaped band around the stapes footplate). This leads to a weakening of the vibration transmission to the perilymph of the inner ear. The contraction of the muscle takes place via a reflex ( stapedius reflex ) that is triggered by loud sound and the triggering of which can be measured with a tympanometer . The contraction of the muscle can also be done arbitrarily by some people.

The stapedius muscle is the smallest striated muscle in the human body .