Anatomy of the Outer Ear
This first and most visible component, the Outer Ear, is comprised of the external fleshy part of the ear and the ear canal; they can be thought of as a radar station, collecting sounds and channeling them to the next component.
Changes here, such as heavy accumulations of wax or infections, can result in significant losses of conductive hearing. These losses, however, are usually temporary and can be cleared up with correction of the condition. Other conditions such as bony growths in the ear canals (common to surfers) can result in much conductive hearing loss. These, however, can be readily corrected through surgery.
Some birth defects restrict the development of the ear canal and result in maximal loss of hearing from birth on. Many of these conditions can also be corrected by surgery today. The condition is called Congential Atresia and can also present some deformity of the external ear termed microtia.
Anatomy of the Middle Ear
This second component is made up of the three bones of hearing and the ear drum. They can be thought of as the conversion element in the hearing/balance process.
The vibration of the ear drum (called the tympanic membrane) resembles the vibration issued from a drum head; the vibration’s energy is transferred to the three bones of hearing:
- the malleus (hammer), striking on
- the incus (anvil) and activating
- the stapes (stirrup) which vibrates in and out of an oval window.
Vibration here enervates the fluids in the inner ear’s cochlea.
The ear drum can be perforated by an accidental injury and bring on infection or other injuries and hearing loss. The repair of the ear drum (called tympanoplasty) is a common surgical avenue for restoration of hearing.
Damage or disruption of the functioning of the bones of hearing are also repairable. Certain conditions may limit the actual movement of those bones, thus limiting the transmission of sound waves. A deposit of bone may fixate the stapes bone. This process is called otosclerosis; the abnormal bone fixes the stapes in position, not allowing it to vibrate properly.
Conductive hearing loss follows.
The reconstruction of the bones of hearing is known as ossiculoplasty and may involve replacement of the incus and/or the stapes bone. These are yet other successful surgical procedures.
Anatomy of the Inner Ear
The final component is the inner ear, the transmission and broadcasting portion of the hearing process. The main structure is the cochlea, a bone that is shaped much like a spiral seashell, and the semicircular canals which are further connected to the brain by the eighth nerve. The cochlea contains nerve endings which deliver hearing impulses to the brain; the nerve endings of balance are in the semicircular canals. The eighth nerve can be thought of as a communications cable connecting the receptors of the inner ear with the information processing centers of our internal computer, the brain.