it consists of a cave, which is at the two sides of the head.This Paukenhöhle (Cavum tympani) develops embryonal from the first throat bag. It is filled and over the Eustachi tube (ear trumpet ) connected with the throat area with air. Over the Eustachi tube a pressure balance finds opposite the external worldinstead of.
in the tympanic cavity are the tiny auditory ossicles, which connect the external ear with the interior ear. Against the drum skin (Membrana tympani) the hammer ( Malleus) rests, to these is connected with the anvil (Incus), which stands again with the stirrup (Stapes) in contact. The stirrup affects the oval window (Fenestra ovalis or vestibularis) of the interior ear (Auris interna).
The auditory ossicles are mobile by fine volumes and muscleshung up. They form a lever system, which transfers the oscillations of the drum skin mechanically to the interior ear. Here an impedance transformation is made: Low sound pressure and high acoustic velocity at the drum skin are transformed into high pressure and low fast ones at the interior ear. Under normal conditions is this coupling optimally, about 60% of the entire sound power by the drum skin to the interior ear are transferred.
tympanic cavity muscles
by two small muscles the characteristics of the sound transmission can be changed: The Musculus tensor tympani sets at the hammerand the drum skin stretches. The Musculus stapedius sets at the stirrup and tilts the stirrup plate in the oval window. Thereby the coupling of the drum skin is worsened to the interior ear, it no more the entire sound power to the interior ear will not transfer,separate a part at the drum skin one reflects and/or. into the surrounding bones derived. Thereby the hearing within certain limits can protect itself against a damage by to high sound pressure.
Stretching this muscles takes place via the so-called Stapediusreflex with volumesfrom over 80-100 railways and about 50 ms are effective after employment of the sound. The Stapediusreflex works at both ears, even if only one ear with high volume is exposed to sound. By an impedance measurement of the outside Gehörgang one knows the employmentthe Stapediusreflexes observe and this for diagnostic purposes use.