Understand How Hearing Works in 9 Q&As

2. What are the main parts of the human ear?

The human ear is divided into three mains parts: the outer ear, the middle ear and the inner ear.

• Hearing Review - Image Diversity: the human ear

3. What structures form the outer ear? What is its function?

The outer ear consists of the pinna, or auricle, and the auditory canal. Its function is to transmit sound waves to the tympanum.

4. What elements form the middle ear? What are the names of the three middle ear ossicles that are involved in phonosensitivity?

The middle ear is made up of the tympanum, the ossicular chain and the oval window. The functional ossicles of the middle ear are the hammer (malleus), the incus and the stapes.

• Hearing Review - Image Diversity: middle ear ossicles

5. What is the tympanum? In which part of the ear is it located and what is its function?

The tympanum (or eardrum) is a membrane located in the middle ear just after the auditory canal, which separates the middle ear from the outer ear. The function of the tympanum is to vibrate with the same frequency of the sound waves that reach it.

6. How are vibrations captured by the tympanum transmitted through the ossicular chain of the middle ear?

The acoustic transmission from the outer to the middle ear (and to the internal ear too) is entirely mechanical. The vibration of the tympanic membrane triggers the vibration of the hammer, which then causes the incus to vibrate. The incus then causes the stapes to vibrate.

7. Why do you feel a change in pressure inside your ear when you go down a mountain?

The pressure inside the middle ear is maintained equal to the outer ear (as well as to the exterior environment) due to a communicating duct between the middle ear and the pharynx called the auditory tube, or Eustachian tube. When someone goes down a mountain, the air pressure upon on the middle ear increases and it is necessary to do exercises such as fake swallowing to force the opening of the pharyngeal orifice of the auditory tube to equalize the pressure once again.

8. What elements make up the inner ear? What are the functions of those structures?

The inner ear is made up of the cochlea and the semicircular canals. The fluid that fills the cochlea receives vibrations from the ossicular chain of the middle ear and transmits the pressure to the semicircular canals. Within the semicircular canals, the pressure variation of the filling fluid moves cilia of the hair cells of these structures. The hair cells then generate action potentials that are transmitted to the brain through the auditory nerves.

• Hearing Review - Image Diversity: inner ear auditory pathway

9. What is the vestibular system? How does it operate?

The vestibular system is the part of the ear that participates in the control and regulation of the equilibrium of the body (balance).

The semicircular canals of the inner ear are placed perpendicularly and detect changes in the gravitational position of the head (this is another sensorial function of the inner ear, besides auditory perception). When the head rotates the pressure of the fluid within the canals upon the cilia of specific receptor cells varies and these cells generate action potentials transmitted by the vestibulocochlear nerve. The neural impulse is then interpreted by the brain as information on the gravitational position of the head.

• Hearing Review - Image Diversity: vestibular system