Introduction

The middle ear consists of the eardrum (tympanic membrane) and an air-filled chamber containing a chain of three bones (ossicles) that connect the eardrum to the inner ear (see Section 19, Chapter 217). The fluid-filled inner ear (labyrinth) consists of two major parts: the organ of hearing (cochlea) and the organ of balance (vestibular system, which consists of the semicircular canals, the saccule, and the utricle). The middle ear acts as an amplifier of sound, while the inner ear is a transducer, changing mechanical sound waves into an electrical signal that is sent to the brain via the nerve of hearing (statoacoustic nerve). Middle and inner ear disorders produce many of the same symptoms, and a disorder of the middle ear may affect the inner ear and vice versa.