Externuskanalen

Externuskanalen, in English the external auditory canal (EAC), is the tube that forms the outer portion of the ear canal and conducts sound from the external environment to the tympanic membrane. In adults it is about 2.5 cm long and roughly 0.7 cm in diameter at its narrowest points. The canal has two regions: a lateral cartilaginous part and a medial bony part, creating a gentle S-shaped curve from the opening at the external auditory meatus to the eardrum.

The canal is lined with thin stratified squamous epithelium and contains hair follicles, sebaceous glands, and ceruminous glands in the lateral portion. These glands produce cerumen, or earwax, which helps trap dust and provides some antimicrobial protection. The outer part is flexible due to cartilage, while the inner part is rigid bone, with the skin loosely adherent in places.

Nerve supply comes primarily from the auriculotemporal nerve (a branch of the trigeminal nerve) and contributions from the auricular branches of the vagus and facial nerves. Blood supply is via the deep auricular artery (a branch of the maxillary artery) and small branches from the posterior auricular and superficial temporal arteries.

Clinical relevance includes otitis externa (inflammation of the canal), otomycosis (fungal infection), and cerumen impaction. Trauma from improper cleaning or foreign bodies can damage the canal, potentially leading to infection or tympanic membrane injury. Management emphasizes gentle cleaning, avoidance of cotton swabs, and topical treatments such as antibiotics or antifungals as indicated, with systemic therapy for complications in high-risk individuals.