TYMPANIC MEMBRANE

also calledeardrum, membrane in the human ear that receives sound vibrations from the outer air and transmits them to the auditory ossicles, which are tiny bones in the tympanic (middle ear) cavity. It also serves as the lateral wall of the tympanic cavity, separating it from the external auditory canal. The membrane lies across the end of the external canal and looks like a flattened cone with its tip (apex) pointed inward. The edges are attached to a ring of bone, the tympanic annulus. Accurate diagnosis of middle-ear diseases is dependent on the appearance and mobility of the tympanic membrane, which is normally pearl gray but is sometimes tinged with pink or yellow. The drum membrane has three layers: the outer layer, continuous with the skin on the external canal; the inner layer, continuous with the mucous membrane lining the middle ear; and, between the two, a layer of radial and circular fibres that gives the membrane its tension and stiffness. The membrane is well-supplied with blood vessels, and its sensory nerve fibres make it extremely sensitive to pain.