Eardrum

From Freepedia

The tympanum or tympanic membrane, colloquially known as the eardrum, is a thin membrane that separates the outer ear from the middle ear. Its function is to transmit sound from the air to the ossicles inside the middle ear. The malleus bone connects the eardrum to the other ossicles.

Rupture of the eardrum can occur in infection, trauma (e.g. by trying to clean the ear with sharp instruments), explosion or loud noise. This leads to conductive hearing loss.

Development

The tympanic membrane forms from the joining of the expanding first pharyngeal pouch and groove. Around day 30 of gestation, the endoderm-lined first pharyngeal pouch 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 mesoderm, the tympanic cavity and external auditory meatus join to form the tympanic membrane. As a result, the tympanic membrane is one of very few adult structures that is derived from all three germ layers.

Sensory system - Auditory system	Edit
Pinna - Ear canal - Eardrum - Ossicles - Cochlea - Basilar membrane - Organ of Corti - Hair cells - Auditory nerve - Primary auditory cortex