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Tensor Tympani Muscle: A (Voluntary) Impedence Modulator In Mammals?

Federico Maria Gioacchini, Elisabetta Genovese, Daniele Monzani, Livio Presutti and Matteo Alicandri-Ciufelli

At the present time, the function of the Tensor Tympani Muscle (TTM) remains unknown. It seems to share many movements in common with the Tensor Veli Palatini (TVP) muscle, so one of the main hypotheses accredited in the literature interprets the TTM as a muscle that, together with the TVP, produces internal deflection of the tympanic membrane breaking the mucous membrane seal of the isthmus of the Eustachian tube, thereby contributing to middle ear ventilation. Some authors have demonstrated its response to loud sounds and vocalizations, chewing, swallowing and external stimulation of the facial muscles.

In the authors’ opinion, and based on evolutionary and physiological considerations, it is possible that the TTM might have acted in mammals to create favourable compliance and impedance conditions in the tympano-ossicular system, so as to hear and transmit high frequency sounds and ultrasounds. Clearly, that function of impedance modulator in humans would have been lost, due to the absence of a sensorineural system to analyse ultrasounds.