Walls of tympanic cavity

The tympanic cavity (a.k.a. middle ear cavity) resembles a box-like space which is situated within the petrous part of temporal bone. It has anterior, posterior, medial, lateral, superior and inferior walls to it. The important relations of walls of tympanic cavity are described below:

• The anterior or the carotid wall is incomplete above due to the opening for pharyngotympanic (eustachian) tube, while below it separates middle ear cavity from the internal carotid artery in front.

• The posterior or the mastoid wall is also incomplete above due to communication of the epitympanic recess with the mastoid antrum.

• The lateral or the membranous wall is related to the tympanic membrane below, while the upper lateral wall is bony which bounds the epitympanic recess.

• The inferior wall (floor) or the jugular wall is a thin bony layer which separates the tympanic cavity from the internal jugular vein.

• The roof or the tegmental wall refers to a thin bony layer which is called tegmen tympani. It separates tympanic cavity from the middle cranial fossa.

• The medial or the labyrinthine wall of the tympanic cavity, is in fact, the lateral wall of the inner ear or the labyrinth. It is characterized by a rounded bulge called the promontory, created by the basal coil of the cochlea. It has tympanic plexus lying on it, that receives contributions from tympanic branch of glossopharyngeal nerve and internal carotid artery plexus, while gives off a lesser petrosal nerve that is destined to reach the otic ganglion. Other important structures within the medial wall include the oval and round windows. The oval window serves as the site of attachment of stapes. In addition, posterosuperior to the oval window, we can also see prominences of facial and lateral semicircular canals.