Tympanic Membrane: Function, Anatomy, and Injury

The tympanic membrane, more commonly known as the eardrum, is a thin layer of tissue separating the outer ear from the middle ear. This structure is responsible for the sense of hearing by receiving sound vibrations from the outside air and transmitting them to the small bones located in the middle ear.

Anatomy and Function of the Eardrum

A healthy eardrum has a pearl-gray appearance and measures about one centimeter in diameter. Its structure is composed of three distinct layers of tissue. The outer layer is continuous with the skin of the external ear canal, while the inner layer is continuous with the mucous membrane that lines the middle ear cavity. Between these is a middle layer made of fibrous tissue that provides the membrane its tension and stiffness.

The manubrium of the malleus, one of the small bones of the middle ear, attaches to the medial surface of the tympanic membrane. This attachment pulls a portion of the membrane inward, creating its characteristic conical shape. The central and most depressed point of this cone is known as the umbo. This shape and the tension of the membrane are factors in how it responds to sound waves.

The primary role of the tympanic membrane is to convert sound waves into mechanical vibrations. When sound waves travel down the ear canal, they strike the eardrum and cause it to vibrate. These vibrations are then transferred to the small bones in the middle ear, starting with the malleus, and then transmitted to the inner ear where they are converted into nerve signals that the brain interprets as sound.

Common Conditions and Injuries

The most frequent issue affecting the eardrum is a perforation, which is a tear or hole in the membrane. A perforation can result from several circumstances, including:

• Middle ear infections (otitis media), where fluid pressure builds and ruptures the membrane. This is particularly common in children.
• Barotrauma, which is a rapid change in pressure between the outer and middle ear from activities like scuba diving or flying.
• Acoustic trauma from loud noises, such as an explosion, that create a powerful pressure wave.
• Direct physical injury from inserting objects like cotton swabs or other items too far into the ear canal.

Over time, the eardrum can also develop scarring, a condition known as tympanosclerosis. This condition involves the formation of dense, white patches on the membrane. While often having little effect on hearing, extensive scarring can sometimes lead to a degree of hearing loss.

Symptoms and Diagnosis

The signs of an eardrum injury often involve distinct auditory and physical sensations. Common symptoms of a perforated eardrum include:

• A sharp, sudden ear pain that may quickly subside after the rupture.
• Hearing loss, which can range from slight to significant depending on the size of the tear.
• Tinnitus, which is a ringing or buzzing sound in the ear.
• Drainage from the ear canal that may be clear, pus-filled, or bloody.
• Feelings of vertigo or dizziness if the injury affects the inner ear.

To diagnose a problem with the tympanic membrane, a physician will use an otoscope. This instrument provides a magnified, illuminated view of the ear canal and eardrum, making it possible to see any perforations, inflammation, or fluid. A test called tympanometry may also be performed, which measures the movement of the eardrum in response to changes in air pressure to confirm a perforation or detect fluid in the middle ear.

Treatment and Healing Process

In many cases, a small perforation in the tympanic membrane will heal on its own over several weeks to a few months. To facilitate healing and prevent complications, it is important to keep the affected ear dry. This means avoiding swimming and using caution when showering to prevent water from entering the ear canal.

If an ear infection is the underlying cause of the perforation, a doctor may prescribe antibiotics. This treatment clears the infection, which reduces inflammation and pressure in the middle ear, creating a better environment for the eardrum to heal. Pain relievers may also be recommended to manage discomfort.

For larger perforations that do not close on their own, surgical repair may be necessary. One common procedure is a myringoplasty, where a surgeon places a patch over the hole in the eardrum. A more complex procedure, tympanoplasty, involves grafting a small piece of the patient’s own tissue onto the eardrum to repair the hole.