The tympanic membrane (also tympanum or myrinx), colloquially known as the eardrum, is a thin membrane that separates the external ear from the middle ear. Its function is to transmit sound from the air to the ossicles inside the middle ear. The malleus bone bridges the gap between the eardrum and the other ossicles. Rupture or perforation of the eardrum can lead to conductive hearing loss. Development The eardrum forms from the joining of the expanding first pharyngeal pouch and groove. Around day 30 of gestation, the endoderm-lined first expands to form the tympanic cavity, which subsequently envelops the inner ear ossicles. Simultaneously, the first pharyngeal groove, which is lined with ectoderm, expands to form the developing external auditory meatus. Separated by a thin layer of splanchnic mesoderm, the tympanic cavity and external auditory meatus join to form the tympanic membrane. As a result, the