The ear consists of 3 parts:
- External Ear
- Middle Ear
- Inner Ear
The external ear
consists of the auricle and auditory canal. The external ear collects sound waves and directs them into the middle ear. The auricle collects sounds from every direction. The ear canal, or external auditory meatus, carries sound to the eardrum.
The middle ear
lies between the external ear and the inner ear. It consists of an air-filled cavity and includes the auditory ossicles. The middle ear consists of:
1. Ossicles in the form of three small bones:
These three bones are connected. The malleus is directly connected to the eardrum, while the stapes is connected to the inner ear. As sound waves vibrate the eardrum, it in turn moves the malleus, which transmits the vibrations via the incus to the stapes. These vibrations are then ultimately transmitted to the membrane-covered opening that leads from the middle ear to the vestibule of the inner ear, called the oval window.
2. The Eustachian tube is a narrow passage leading from the pharynx to the cavity of the middle ear, permitting the equalization of pressure on each side of the eardrum.
The inner ear
is made up of two parts:
- Cochlea for auditory portion
- Semicircular canal and otolithic organ for balance and motion
consists of hair cells, sensory cells and fluid-filled spaces. Oscillations in the middle ear set the fluid in the cochlea in motion. Hair cells in the cochlea perform the transduction of the sound waves into electrical impulses. Auditory nerve fibers transmit these electrical signals along the auditory nerve and eventually on to the brain stem for translating and processing.