Trommelfells

Trommelfells, or tympanic membranes, are thin, cone-shaped membranes that separate the external auditory canal from the middle ear. Each membrane is approximately 8–10 mm in diameter and consists of three layers: an outer epithelial layer continuous with the skin of the ear canal, a middle fibrous layer with radial and circular collagen fibers, and an inner mucosal layer facing the middle ear. The membrane is taut and the umbo marks the point where the handle of the malleus attaches.

The primary function of the tympanic membranes is to convert sound waves in the ear canal into mechanical vibrations that are transmitted through the auditory ossicles (malleus, incus, stapes) to the inner ear. In addition to this vibration transfer, the tympanic membranes contribute to impedance matching between air and the fluid-filled cochlea, helping to amplify pressure reaching the inner ear.

Sensation of the external surface is primarily provided by the auriculotemporal nerve, a branch of the trigeminal nerve, while the inner surface is supplied by nerves associated with the tympanic plexus, including components of the glossopharyngeal nerve.

Vascular supply comes from branches of the maxillary artery, with the outer (lateral) surface mainly supplied by the deep auricular artery and the inner (medial) surface by vessels associated with the tympanic plexus.

Clinical relevance: trommelfells can be perforated by trauma or acute otitis media, barotrauma, or chronic infection, causing conductive hearing loss. Perforations may heal spontaneously or be repaired surgically by tympanoplasty. Embryologically, the tympanic membranes arise from ectoderm and endoderm with a middle-layer mesenchymal core during early fetal development.