Auditory Overview

Hearing is among the important senses that provide perceptions to human beings about environmental stimuli and conditions outside of the human body. The auditory system is composed of the structures of the ear related to perception and reception of sound (peripheral auditory system), and the organization and meaning designated to the sounds heard (central auditory system). The ear, the organ of hearing, is the main component of the auditory system. The ear has a dual function; hearing and maintenance of equilibrium. The structures of the ear consist of the external, the middle, and the inner ear. The auricle and the external auditory canal are parts of the external ear. The auricle is the part of the ear that is not enclosed in the head. The middle ear includes the tympanic membrane and the small ear bones (ossicles) named the malleus, incus, and stapes. The ossicles are joined together and extend from the tympanic membrane to the oval window. The middle ear communicates with the eustachian tube, the nasopharynx, and the mastoid cells in the mastoid bone. The external and middle portions of the ear serve to conduct and amplify sound waves received from the environment. The inner ear structures include the semicircular canals, cochlea, and auditory nerve (vestibulocochlear nerve). The receptor organ for hearing is the cochlea, and the semicircular canals contribute to the maintenance of balance. Sound is transmitted to the inner ear and picked up by the cochlea. The impulses initiated are then carried by nerve fibers to the acoustic portion of the VIIIth cranial nerve, and then to the brain.