About the Ear
The pinna is the visible part of the ear that resides outside of the head. The primary purpose of the pinna is to collect sound. It does so by acting as a funnel, amplifying the sound and directing it to the ear canal. When sound passes through the pinna, it goes through a filtering process in which sounds in the frequency range where human speech is normally found are enhanced.
The ear canal has two main functions:
-Provides a passageway for sound to travel from the pinna to the eardrum
-Protects the ear from infection. On average, the canal is about 3.5 cm long and 0.7 cm wide. Old skin is pushed out when new skin grows, naturally cleaning the ear canal. Further in, the canal contains small hairs that filter out debris. The only thing that is able to successfully pass through the auditory canal is the sound itself, which then continues to the eardrum.
The eardrum plays an important role in hearing. At about 1 cm in diameter, the eardrum consists of three layers of different materials. The layer closest to the auditory canal is composed of skin; the next layer is of a fibrous and elastic material; the final layer is a mucus producing lining. The eardrum vibrates when impacted by sound waves that have travelled through the ear canal, and then transfers these vibrations to the middle ear.
The ossicles are three tiny bones called the malleus, incus, and stapes, or also called the hammer, anvil, and stirrup due to their shapes. These three tiny bones transfer the vibrations of the eardrum to the inner ear.
The hammer-shaped bone that is outermost of the three ear bones in the middle ear.
An anvil-shaped bone located between the malleus and the stape in the middle ear.
The innermost of the three small bones in the middle ear, which is somewhat shaped like a stirrup.
The oval window is a membrane in the wall of the cochlea. Vibrations from the stapes in the middle ear are received and transferred to the fluid of the cochlea.
The cochlea is part of the Inner Ear. The cochlea is responsible for converting sounds which enter the ear canal, from mechanical vibrations into electrical signals. This process, known as transduction, is performed by specialized sensory cells within the cochlea. The electrical signals, which code the sound's characteristics, are carried to the brain by the auditory nerve.
The auditory nerve is a pathway that allows the neural signals produced by the stereocilia in the cochlea to travel to the brain. Once in the brain the signals from both ears are combined, processed, and interpreted to produce the sensation that we call hearing.