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Anatomy and function of the ear

ear anatomy

The human ear is made up of 3 parts; the outer ear, the middle ear and the inner ear.


External ear

The outer ear (on the left in the photo) is made up of the pinna, which is the visible part of the ear and the external ear canal. The pinna acts as a funnel by capturing sounds and directing them to the external ear canal which directs sounds to the eardrum.


Middle ear

The middle ear contains the eardrum and the ossicles, namely the hammer, anvil and stirrup.

The eardrum is a membrane that separates the ear canal from the middle ear cavity. The sound vibrations contained in the air vibrate the eardrum which is attached to the ossicle chain. The movement of the eardrum causes the movement of the 3 ossicles.

The last in the chain, the stirrup, comes into contact with the inner ear. It hits on it in order to transmit the vibrations further into the hearing system.

There is also the eustachian tube which balances the air pressure between the middle ear and the outside. It also provides some protection against the introduction of pathogens into the system and allows their evacuation.


Inner ear

The inner ear is made up of the vestibular system, i.e. the vestibule and the semicircular canals which are responsible for maintaining balance and the cochlea which contains the sensory cells of hearing, called hair cells. The hair cells will transform the physical vibrations into electrical signals which will be transported to the brain, by the auditory nerve, so that the sound heard is interpreted.


Passage of sound; from the outer ear to the brain

The sound produces a vibration of the air. This vibration is captured by the pinna and directed through the external ear canal towards the eardrum. The eardrum then begins to move. This being attached to the ossicles, also causes their movement. The last ossicle in the chain comes into contact with the cochlea which contains the sensory cells of hearing. Hair cells transform physical vibrations into electrical signals. The latter is transported to the brain by the auditory nerve so that the sound heard is interpreted.


Types of hearing loss

There are 3 types of hearing loss; conductive or conductive hearing loss, sensorineural or sensorineural hearing loss, and mixed hearing loss.


Conductive or conductive hearing loss

Conductive hearing loss can be damage to the external ear canal, eardrum, ossicles or middle ear cavity that limits and hinders the passage of sound to the inner ear. It may be a blockage of earwax, a perforation of the eardrum, a dislocation or fusion of the ossicles or even an accumulation of fluid in the cavity of the middle ear. When fluid builds up behind the eardrum, whether it is infected or not, it is an ear infection. Otitis is the most common condition, especially in children.

The majority of conductive disorders can be resolved through treatment or surgery, among others. Additionally, because hearing cells are not damaged, the use of hearing aids may be beneficial. Indeed, a higher volume allows the sounds heard to overcome the hindrance produced by the conductive condition.


Sensorineural or sensorineural hearing loss

This is damage that affects the hearing cells in the cochlea or the nerve pathways behind the cochlea. Several causes are possible such as normal aging, exposure to noise, heredity, a virus or infection, sound or head trauma, among others. In the majority of cases, once hearing cells are damaged, the damage is irreversible and permanent.

One of the solutions considered for this type of deafness is the wearing of hearing aids adapted and adjusted to the person's hearing.


Mixed hearing loss

This is a hearing loss that integrates the two other types of deafness. It brings together a condition in the outer ear or the middle ear in addition to damage to the hearing cells.

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