Anatomy and Physiology of the Ear
What is the ear?
The ear is the organ of hearing. The parts of the ear include:
External or outer ear
The external ear consists of:
- Pinna or auricle - the outside part of the ear.
- External ear canal - the canal that connects the outer ear to the inside or middle ear.
- Tympanic membrane - also called the eardrum. The tympanic membrane divides the external ear from the middle ear.
Middle ear (tympanic cavity)
The middle ear consists of:
- A cavity that usually contains air
- Ossicles - three small bones that are connected and transmit the sound waves to the inner ear. The bones are called:
- Eustachian tube - a canal that links the middle ear with the throat area. The eustachian tube helps to equalize the pressure between the middle ear and the air around you. Having the same pressure allows for the proper transfer of sound waves. The middle ear cavity and eustachian tube are lined with mucous membrane, just like the inside of the nose and throat.
The inner ear onsists of:
- Cochlea (contains the receptors for hearing)
- Vestibule (contains the receptors for balance)
- Semicircular canals (contain the receptors for balance)
How do we hear?
Hearing starts with the outer ear. When a sound is made outside the outer ear, the sound waves, or vibrations, travel down the external ear canal and strike the eardrum (tympanic membrane). The eardrum vibrates. The vibrations are then passed to the three tiny bones in the middle ear called the ossicles. The ossicles amplify the sound and send the sound waves to the inner ear and into the fluid-filled hearing organ (cochlea).
Once the sound waves reach the inner ear, they are converted into electrical impulses that the auditory nerve sends to the brain. The brain then translates these electrical impulses into the perception of sound.
Reviewed by: Steven D. Handler, MD, MBE
Date: April 2009