General Description of the Parts of the Ear
The outer ear consists of the external ear or visible ear, and the auditory canal. The auditory canal is the narrow tube that leads from the opening in the ear to the eardrum.
The external ear traps sound waves in the atmosphere and directs the sound into the ear canal where it travels the length of the tube, pressing against the eardrum.
The middle ear extends from the eardrum, at the end of the ear canal, to the oval window located at the wall separating the middle ear from the inner ear.
The middle ear contains the eardrum, the ossicular chain, a group of three small bones which extend from the eardrum to the oval window, the oval window itself, the round window, and the middle ear cavity which extends upward from the Eustachian tube leading from the back of the throat.
The middle ear transmits and amplifies sound which it receives from the outer ear.
The lower part of the inner ear contains a bony labyrinth which is formed in the shape of a spiral coil or snail shell, known as the cochlea. The cochlea contains the auditory receptors for separating sounds into their constituent vibrations, and for converting the vibrations into neurochemical impulses.
After the sounds have been analyzed, and converted to neural pulses, they are transmitted along the acoustic nerve, eventually passing through the various auditory regions of the brain, where they are processed as sound perceptions.
The upper part of the inner ear contains the semicircular canals, which is a bony circular-shaped structure filled with fluid that extends outward in each of the three x, y, z dimensions. In addition, there are two otolith organs which are located just below the semicircular canals, above the cochlea. Together, the semicircular canals and otolith organs contribute to our sense of balance and to our ability to maintain posture, to sit upright, and to know what position our bodies are in when we are moving.