The tympanic cavity (latin: cavitas tympani) is a narrow, irregular space located in the petrosal part of the temporal bone and situated between the external and the internal ear. The tympanic cavity houses three ossicles that provide conduction and amplification of sound vibrations from the tympanic membrane to the inner ear.
The tympanic cavity has a vertical diameter of around 18 mm, an anteroposterior diameter of around 10 mm and a transverse diameter of 3 to 5 mm. The tympanic cavity is lined by mucosa with a cylindrical or layered cubic epithelium interspread with ciliated cells. The epithelium changes to pseudo-stratified ciliated epithelium, as it is through the entire length of the auditory tube.
The tympanic cavity can be divided into three parts - epitympanum (or attic space), mesotympanum and hypotympanum.
The borders forming the walls of the tympanic cavity are as following:
- tegmental wall (roof) is formed by the tegmen tympani;
- jugular wall (floor) is formed by a bone that separates the middle ear from the internal jugular vein;
- membranous wall (lateral wall) is formed mostly by the tympanic membrane and the bony wall of the epitympanic recess;
- labyrinthine wall (medial wall) separates the middle ear from the inner ear; it includes the promontory of the labyrinthine wall and the oval and round windows;
- carotid wall (anterior wall) separates the tympanic cavity from the carotid canal and artery; it has an opening called the aditus to the mastoid antrum that connects the tympanic cavity to the mastoid cells.
The tympanic cavity surrounds the three auditory ossicles: malleus, incus and stapes.