trommehinnens

Trommehinnens, in medical terminology, refer to the tympanic membranes or eardrums. Each ear contains one tympanic membrane that separates the external auditory canal from the middle ear. The membranes are thin, semi-transparent structures whose outer surface faces the ear canal and inner surface faces the middle ear. They are roughly 8–10 millimeters in diameter and about 0.05–0.1 millimeters thick. The tympanic membrane has three layers: an outer cutaneous layer, a fibrous middle layer that provides stiffness, and an inner mucous layer. The edge is attached to the tympanic ring (annulus) surrounding the ear canal, and the handle of the malleus (the first auditory ossicle) is firmly embedded in its inner surface. The membrane is conventionally divided into pars flaccida (superior, more flexible) and pars tensa (lower, taut portion).

When sound waves reach the ear, the eardrum vibrates in response to air pressure variations. These vibrations are transmitted via the auditory ossicles to the inner ear, where they are converted into neural signals. The eardrum also serves as a protective barrier against foreign matter and infection.

Clinically, perforation or scarring of the tympanic membrane can cause conductive hearing loss and increases the risk of middle-ear infection. Conditions such as otitis media or trauma may require medical treatment or surgical repair (tympanoplasty) or the insertion of tympanostomy tubes in chronic cases. Tympanometry and otoscopy are common techniques for assessing tympanic membrane function.

Evolutionarily, the tympanic membrane is a feature of many land vertebrates in which it functions in hearing, with variations among species.