anatomy of the outer ear

Last reviewed 01/2018

The outer ear collects sound and directs it towards the tympanic membrane. It is lined with skin and consists of the cartilaginous pinna and a canal, the external auditory meatus.

The ear canal measures 2-3 cm in adults and the outer part is curved downwards requiring the pinna to be pulled upwards and outwards during examination. The outer one third is cartilaginous; the inner two thirds, bony. In children, the canal is shorter and relatively straight.

The bony inner part of the canal is lined by highly specialised stratified squamous epithelium which is devoid of hair cells and does not desquamate. Uniquely, this skin shows the property of lateral migration - an active process, starting at the tympanic membrane, which serves to keep the ear canal clean and at it's most efficient, for air conduction. The skin migrates at about 100 micrometres per day.

Attempts by patients to clean the ear with cotton buds serves only to frustrate this natural process.

The skin covering the cartilaginous part of the canal is similar to that elsewhere in the body. It contains sebaceous and ceruminous glands which together, make wax. Wax is oily and serves to prevent dirt and dust entering the ear. As this part of the ear canal only contains hair follicles, it is the location where boils may occur.

Lymph nodes which drain the external ear are the retroauricular, parotid, retropharyngeal and upper deep cervical nodes. Enlargement of these node may be due to an infection or neoplasm in the external ear.