Middle Ear

Middle Ear is known as the tympanic cavity (lined with simple cuboidal epithelium). Its main function is converting sound waves arriving from the external ear into mechanical vibrations that are transmitted to the internal ear. It contains three auditory ossicles (malleus, incus, and stapes), muscles attached to the ossicles, auditory tube, round window, and oval window.

• The auditory tube connects the middle ear to the nasopharynx. It is lined with ciliated pseudostratified columnar epithelium. It vents to the middle ear, equalizing pressure of the middle ear with atmospheric pressure. Walls of the tube are normally compressed, which open when yawning or swallowing. It may serve as a route for spread of infections from the pharynx to the middle ear (otitis media).

Tympanic membrane separates the middle ear from the external acoustic meatus. It transmits sound waves to the ossicles of the middle ear. The layers of the tympanic membrane are:

• Skin of the external auditory canal (stratified squamous keratinized)
• Core of radially and circularly arranged collagen fibers
• Epithelial lining (mucous membrane) of internal surface (middle ear side), made of low simple cuboidal epithelium