Transpetrosal approach to middle ear cavity. This view of a right middle ear cavity reveals several relationships of structures within this space. Along its lateral wall is the tympanic membrane to which is attached the handle/manubrium of the malleus. Between the handle of the malleus and long crus of the incus the chorda tympani arches through this space from its posterior wall (right border of image) toward its anterior wall (left border of image). The roof of the internal auditory canal and medial wall of the tympanic cavity have been removed to reveal the facial nerve (and its labyrinthine, tympanic, and mastoid segments), the geniculate ganglion, the greater superficial petrosal nerve, and the oval window (at baseplate of stapes bone). The tensor tympani muscle has been dissected from its semicanal and its tendon is shown coursing across the cavity to attach to the neck of the malleus. It functions to reflexly draw the tympanic membrane medially to dampen loud sounds and to protect the organ of hearing. (Image courtesy of AL Rhoton, Jr.)