CHAPTER 26 - THE EAR

Abstract

This chapter discusses the ear and its parts, which consist of the external ear, the middle ear, and the inner ear. The inner ear is involved with equilibration and the perception of motion. The external ear receives the sound waves, which are transmitted to the middle ear. The middle ear transmits the vibrations, which are received by the inner ear. The nerve impulses originate in the inner ear, which are perceived by the central nervous system as sound. The external ear consists of the auricle, the external auditory meatus, and the tympanic membrane. The middle ear consists of the tympanic cavity, which is an air-containing space in the petrous part of the temporal bone. It communicates with the nasopharynx by the pharyngotympanic tube and is bridged across by three ossicles. The inner ear consists of the bony labyrinth containing perilymph in which is suspended the membranous labyrinth containing endolymph. The bony labyrinth, hollowed out of the petrous part of the temporal bone, comprises the vestibule, the semicircular canals, and the cochlea; it is lined by a layer of flattened cells that covers the periosteum. One branch of the auditory artery supplies the bony labyrinth, and another supplies the membranous labyrinth.