Corpus: Stapedius muscle

The stapedius muscle is the smallest striated muscle in the human body, measuring around 7 mm in length. Together with the tensor tympani muscle, it is one of the middle ear muscles.

The stapedius muscle has its origin at the eminentia pyramidalis within the cavitas tympani (tympanic cavity). The tendon extends laterally and attaches to the caput and crus posterius of the stapes.

Innervation takes place via the stapedius nerve, a branch of the facial nerve. It runs between the stapedius muscle, the malleus and the incus.

The stapedius muscle is able to tilt the stapes dorsally, tilt the foot plate of the stapes in the fenestra ovalis and thus tighten the anular stapedial ligament. Contraction of the muscle thus leads to attenuation of the vibrations in the oval window. This mechanism enables the organism to desensitise the sense of hearing during speech production and to adjust the sensitivity of the auditory system.

see also: Stapedius reflex

Paralysis of the stapedius muscle (e.g. in the context of facial nerve palsy) leads to an increased reaction of the stapes to sound vibrations and thus to hyperacusis.