The eardrum is a thin, smooth, white layer of tissue about 2.5 cm from the external canal opening and about 0.2 mm thick. It can be divided into the tense tympanic membrane and the relaxed tympanic membrane. The relaxed tympanic membrane is rich in blood vessels, while the tense tympanic membrane can be divided into the light cone, the hammer bone stalk, and the short protrusion of the hammer bone. When external light shines into the ear, the light cone can cause light reflection, so when people see a bright inside outside the ear, it is the result of the reflection of the light cone of the tympanic membrane. The tympanic membrane plays a key role in human hearing by sensing external sounds, which are then transmitted to the auditory chain, inner ear, and auditory nerve, causing human hearing to be conducted.