Middle ear

The middle ear includes/understands the tympanum ( tympanum ), as well as the ossicles (the “chain ossiculaire”), four very small Os. They are called respectively the hammer ( maleus ), the anvil ( incus ), the lenticular Os (which is the smallest bone of the human body) and the clamp ( pillars ). These names come from their characteristic forms. The hammer and the anvil form a not very flexible articulation called block incudo-maléaire.

The sounds are the result of vibrations of the air in the auditory canal which cause to make vibrate the tympanum. These vibrations will be then transmitted to the ossicles then with the internal ear via the oval window.

The design which currently dominates over the propagation of the vibrations in the middle ear is that of Khana and Tonndorf, elaborate in 1972: schematically, the lines of the concentric zones of Iso-amplitude of certain frequencies are parallel to the handle of the hammer, with, for the membrane of the tympanum, the zones of vibration fuller than for this handle.

Since the middle ear is hollow, an environment of high pressure (as water) would pose the risk to burst the tympanum. To mitigate this risk is the function of the Eustachian tubes. Descendants évolutionnaires of respiratory hearing of the Poisson S, these horns connect the middle ear to the nasal fossae in order to decompress the middle ears.

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