Changes

*The round window is positioned more caudally, and leads to the cavity of the cochlea.

*The round window is positioned more caudally, and leads to the cavity of the cochlea.

*Sound vibrations are transmitted from the tympanic membrane, across the tympanic cavity, via the ossicles (malleus, incus, then stapes).

*Sound vibrations are transmitted from the tympanic membrane, across the tympanic cavity, via the ossicles (malleus, incus, then stapes).

*The ossicles, as well as transmitting sound vibrations from the tympanic membrane, also magnify the vibrations by about 20 times. This is necessary for initiating waves in the endolymph of the cochlea. The magnification is achieved by the action of two muscles that are attached to the ossicles, and which act as antagonists of each other. These two muscles are the tensor tympani muscle and the stapedius muscle. The tensor tympani muscle originates within the tympanic cavity, and inserts on the malleus. The contraction of this muscle creates tension of the ossicles, and therefore also of the tympanic membrane, all of which results in greater sensitivity. The stapedius muscle originates from the wall of the tympanic cavity, and inserts on the stapes. Contraction of this muscle pulls the end of the stapes away from the oval window, thereby reducing the fource of the transmission of sound vibrations.

*The ossicles, as well as transmitting sound vibrations from the tympanic membrane, also magnify the vibrations by about 20 times. This is necessary for initiating waves in the endolymph of the cochlea. The magnification is achieved by the action of two muscles that are attached to the ossicles, and which act as antagonists of each other. These two muscles are the tensor tympani muscle and the stapedius muscle. The tensor tympani muscle originates within the tympanic cavity, and inserts on the malleus. The contraction of this muscle creates tension of the ossicles, and therefore also of the tympanic membrane, all of which results in greater sensitivity. The stapedius muscle originates from the wall of the tympanic cavity, and inserts on the stapes. Contraction of this muscle pulls the end of the stapes away from the oval window, thereby reducing the force of the transmission of sound vibrations.

*The eustachian tube connects the tympanic cavity to the nasopharynx, which mark the beginning and end of the eustachian tube, respectively.

*The eustachian tube connects the tympanic cavity to the nasopharynx.

*The eustachian tube functions to equalise pressure on either side of the tympanic cavity, by opening while yawning or swallowing, for example.

*The eustachian tube functions to equalise pressure on either side of the tympanic cavity, by opening while yawning or swallowing, for example.