The ear (from the Latin auricula) is the organ of hearing and balance.

The ear is found in an even and symmetrical manner on each side of the head. It is made up of three main regions:

• The outer ear,
• The middle ear,
• The inner ear.

Outer ear

The outer ear is shaped like the pinna and the external auditory canal. The auricle, or auricle, corresponds to what is called in everyday language, the ear: it is the shell-shaped part, made rigid by cartilage except in its lower part, the earlobe, which is made of skin. The horn helps to direct the waves towards the duct.

The duct is a small, narrow tube (approximately 2,5 cm long by 0,5 cm wide) that passes through the temporal bone. Its walls are covered with ceruminous glands which secrete earwax, a yellow-brown substance that traps foreign bodies (dust, bacteria, etc.) present in the duct; this is commonly referred to as wax. The outer ear transmits sound to the inner ear by striking a membrane at the end of the duct, the eardrum.

Middle ear

The middle ear is made up of several air-filled cavities carved into the temporal bone, the main one being the eardrum. It contains the three smallest bones of the human body: the hammer, the anvil and the stirrup. These bones form a chain of ossicles that transmit vibrations from the eardrum to the inner ear.

The middle ear is connected to the throat by the Eustachian tube, a conduit that maintains the same pressure between the middle ear and the outside. It is normally closed but opens when yawning, swallowing or sneezing. People who have already taken the plane know this sensation of the ears which “come loose” when the pressures are balanced.

It communicates with the inner ear through two orifices, the round window and the oval window.

Inner ear

The inner ear is a complex structure called a bone labyrinth. It is actually a cavity that consists of three parts: the cochlea, the vestibule and the semicircular canals. The cochlea is the organ of hearing, in the shape of a spiral. The vestibule is located between the cochlea and the semicircular canals, of which there are three and oriented in the three planes of space. The labyrinth is filled with lymphatic fluids.

The ear is the organ responsible for hearing and for balance. The outer ear and the middle ear are only dedicated to hearing. The inner ear is involved in hearing and balance.

The mechanism of hearing

When a sound wave enters the external ear canal, it hits the vibrating eardrum. These vibrations are transmitted to the chain of the ossicles, which in turn propagate the movement to the fluids in the inner ear. These vibrations reach the cochlea which contains the organ of Corti: it is the receiver of the vibrations which is lined with hair cells sensitive to the movements of the liquid. These cells translate sound movements into nerve impulses. These messages are transmitted by the cochlear nerve to the brain where they are decoded and interpreted.

The human ear perceives sound waves that have a frequency between 20 hertz (low frequencies) and 20 Hertz (high frequencies).

The balance mechanism

Balance is maintained by the vestibular apparatus of the inner ear. The vestibule and the three semicircular canals are lined with hair cells sensitive to movement. When the head moves, the liquid moves and activates the cilia of these cells. They then produce a nervous message sent to the cerebellum to inform about the position of the head. In the hair cells of the semicircular canals, there are small crystals of calcium carbonate (otoliths) suspended in the liquid. While moving, these crystals weigh more or less on the hair cells. Likewise, a message is sent to the brain to inform about the position of the body in space.

Maintaining balance also involves the visual and muscular systems. Depending on all the information received, the brain adjusts posture if necessary by activating certain muscles.

Acouphènes : these are “parasitic” noises that a person hears without them actually existing. It could be hissing, buzzing or clicking, for example. They result from a dysfunction of the auditory nervous system. Temporary tinnitus can occur after exposure to very loud music.

Otitis media : infection or inflammation of the ear. Otitis is said to be “middle” because it affects a small bony cavity in the middle ear, located behind the eardrum. It usually results in ear pain and fever.

Serous otitis : inflammation of the lining of the middle ear causing more or less thick fluid effusion. A viral infection coupled with a bacterial superinfection is usually the cause. Serous ear infections can easily go unnoticed because they do not cause severe pain. The major symptom is hearing loss and its main complication is speech delay. It is very common in children aged 3 to 6 years.

Dizziness : indicates a frequent phenomenon which affects approximately 1 person in 7. It corresponds to a sensation of rotation of our environment, this is why the expression “to have the head which turns” is often used to describe it. The causes of vertigo are multiple; it can reflect a simple benign disease or more serious diseases (see vestibular neuronitis and Ménière’s disease below).

Vestibular neuronitis : often confused with labyrinthitis, it is characterized by the sudden appearance of intense dizziness. The symptoms are so intense that bed rest is often necessary for 2 or 3 days, sometimes up to 1 week.

Labyrinthite : acute inflammation of the inner ear. The patient suffers from fever, ear pain and shows signs of hearing impairment associated with balance disturbances. It can follow a viral infection (the varicella zoster virus) or more rarely a bacterial otitis media.

Ménière’s disease (or Ménière’s syndrome): is characterized by recurrent attacks of dizziness accompanied by wheezing and ringing in the ears (tinnitus) as well as hearing loss.

Cerumen cap : is characterized by the unusual accumulation of earwax in the ear canal. This phenomenon may be due to an increase in the production or poor evacuation of earwax. It can cause hearing loss or ringing, irritation or pain in the ear canal. It is possible to try to dissolve it with physiological serum or sea water but you should not try to remove it with a cotton swab for example in order to avoid damage to the ear canal.

Deafness : Any hearing loss, significant or not, constitutes a form of deafness. Two types of deafness are distinguished.

• Conductive hearing loss: temporary or permanent, it is caused by an obstacle to the propagation of the vibrations of the sound wave to the inner ear. It originates from damage to the outer ear (earwax plugs) or middle ear (otitis, perforation of the eardrum or otosclerosis).
• Sensory deafness: it is due to damage to the inner ear (cochlea) which affects the receptor hair cells, or the auditory nerve or the auditory centers of the brain. The nervous transmission of the sound message is no longer ensured correctly.

Presbycusis : normal aging of the inner ear which begins at age 25 and which results in progressive hearing loss with age. The most frequent cause of deafness in people over 50, it begins with a loss of distinction between high-pitched sounds and then gradually low-pitched sounds.

Hyperacousie : hearing hypersensitivity, sufferers perceive sounds louder than they really are. It affects 2% of the general population and 60% of people already suffering from tinnitus (8). Hyperacusis is usually caused by sound trauma such as a concert, explosion, or prolonged occupational exposure (musical instrument).

Otospongiose (or otosclerosis): genetic disease characterized by remodeling of the third ossicle, the stapes. It undergoes destruction and then during its reformation, it hardens and calcifies which leads to a blockage of the bone. The transmission of the vibrations of the sound wave to the inner ear is therefore stopped. There is no cure. In the most important cases, it is possible to wear hearing aids or to have surgery.

Perforation of the eardrum : it can occur following a trauma (injury with a cotton swab, a slap or a dive for example). It is characterized in particular by intense pain and hearing loss. Healing is usually spontaneous after several weeks. Otherwise, a tympanoplasty can be performed.

Piercings : the pavilion of the outer ear can be pierced to hang earrings or piercings. The lobe, fleshy and composed entirely of skin, constitutes a privileged zone. It is also possible to pierce areas of the cartilage (tragus, helix, etc.).

In children, the eustachian tubes are in a more horizontal position than in adults. During the feeding, it is advisable not to put the baby to bed in order to avoid the entry of milk into the proboscis.

Certain practices can irreversibly damage hearing. In France, 5 million people are hard of hearing, including 2 million under the age of 55 (9). Prevention measures (10) exist to try to reduce these risks. Listening to music with headphones, widely acclaimed today, should be limited to 1 hour per day with a volume set to half the maximum. For activities such as concerts, discos or festivals, the first thing to do is to move away from the speakers and then take sound breaks. For professionals who work in risky trades, such as carpenters, it is advisable to wear a protective helmet.

Otoscopy: visual clinical examination of the ear. The doctor examines the different structures of the ear using specific instruments such as an otoscope. Its end, funnel-shaped and equipped with a lumen, is easily inserted into the external auditory canal to observe up to the eardrum. It makes it possible to highlight a local attack such as a plug of earwax for example.

Audiometry: examination that consists of evaluating hearing, using instruments producing sounds or words that the patient must listen to, detect and sometimes repeat. The results obtained are entered on a curve called an audiogram.

Myringotomy: incision in the eardrum that allows fluid to escape. This procedure is performed in the case of otitis media (evacuation of pus) or serous otitis in order to reduce the pressure in the cavity.

Tympanoplasty: reconstruction of the eardrum after its tearing following a trauma with an object (cotton swab) or frequent infections of the middle ear for example.

Chemical labyrinthectomy: injection of an antibiotic into the middle ear which will diffuse into the inner ear. This antibiotic, gentamycin, has the particularity of being toxic to the vestibule but little to the cochlea (10). This intervention can be offered to people suffering from vertigo in the case of Ménière’s disease.

Vestibular neurectomy: surgical intervention that involves cutting the nerve fibers that carry information from the labyrinth. This type of intervention is offered to people suffering from disabling vertigo linked to a dysfunction of the functions of the balance, and for which the treatments are ineffective.

Scanner: diagnostic imaging technique which consists of “scanning” a given region of the body in order to create cross-sectional images, thanks to the use of an X-ray beam. The term “scanner” is actually name of the medical device, but it is commonly used to name the exam. We also speak of computed tomography or computed tomography. In the case of dizziness, the scanner can visualize the inner ear.

In Greek mythology, to punish Midas, king of Phrygia, for not having designated him the winner of a music competition, Apollo dressed him in real donkey ears, which forced the king to wear a cap for the rest of his life. Big ears would be the sign of stupidity.

Many countries place special significance on the ears, some of which are sexual. In Africa, some ethnic groups in Mali lend the ear a double sex symbol, the pinna being a rod and the ear canal a vagina. In India, on the other hand, having long ears is a sign of wisdom and longevity (13).

Regardless of their size, ears continue to grow throughout life, at a rate of 0,22 mm per year (14).