Ear anatomy

The external auditory canal is a cylinder measuring approximately 2.5 cm in length and 7 to 9 mm in width, extending from the conchal cartilage of the auricle to the tympanic membrane. It is divided into a lateral (outer) cartilaginous portion that occupies approximately one-third of the canal, and a medial (inner) bony portion that occupies the other two-thirds. Their junction is termed the isthmus and is the narrowest region of the ear canal. The outer cartilaginous portion is lined by thicker skin with numerous adnexal structures, including cerumen glands (a modified apocrine type gland), sebaceous glands, and hair follicles. Cerumen is formed here. The inner osseous portion of the canal contains thin skin without subcutaneous tissue. The inferior tympanic recess is a small depression in the inferior medial aspect of the ear canal, adjacent to the tympanic membrane. Debris can collect in this area and cause or perpetuate infection.