trommehinne

Trommehinne, also known as tympanic membrane or eardrum, is a thin, cone-shaped membrane that forms the boundary between the external auditory canal and the middle ear. It converts sound waves into mechanical vibrations that are transmitted to the inner ear via the auditory ossicles.

Anatomy and structure: The membrane is about 8–10 mm in diameter and consists of three layers: an outer cutaneous layer continuous with the skin of the ear canal, a middle fibrous layer (pars tensa) that provides stiffness through radial and circular fibers, and an inner mucosal layer facing the tympanic cavity. The central area is concave and contains the umbo, where the handle of the malleus attaches. The small, more flexible portion above the malleus is the pars flaccida. The outer surface is translucent and pearly gray.

Function: The tympanic membrane vibrates in response to sound pressure, transmitting movements to the ossicular chain (malleus, incus, stapes) and on to the inner ear. It also helps protect the middle ear from debris and pressure changes to some extent.

Nerve supply, blood supply, and development: The outer surface is innervated by branches of the auriculotemporal nerve (CN V3) and the auricular branch of the vagus nerve, while the inner surface is supplied by nerves associated with the tympanic plexus (primarily CN IX). Blood supply comes from branches of the maxillary artery (deep auricular), as well as accompanying vessels around the tympanic cavity. Embryologically, the membrane arises from ectoderm of the external auditory canal, endoderm of the middle ear, and surrounding mesenchyme.

Clinical relevance: Perforations from infection or trauma, chronic otitis media, or barotrauma can affect function. Conditions such as tympanoplasty aim to repair damaged tympanic membrane.