||The anterior wall contains openings for the entry of two structures-the tensor tympani muscle and the eustachian (pharyngotympanic) tube.
The eustachian tube runs anteriorly and medially from the tympanic cavity to the nasopharynx and is responsible for the normal aeration of the middle ear cleft.
A large potential defect in the outer surface of the box is covered by a mobile membrane (the tympanic membrane).
The area inside the box which, lies above the level of the tympanic membrane is the attic or epitympanum.
The area inside the box which lies below the level of the membrane is the hypotympanum
The area inside the box which lies directly medial to the tympanic membrane is the mesotympanum.
The floor of the middle ear is a thin layer of bone which, separates the tympanic cavity from the carotid arteryand the jugular bulb.