External auditory canal: the external auditory canal is a curved pipe that extends from the external auditory canal into the concha cavity to the tympanic membrane, and can transmit the sound waves collected by the auricle to the tympanic membrane in the direction of first inward upward, then inward upward and then inward downward; Adults are about 2.5 ~ 3.5 cm long. Because the tympanic membrane is inclined, the anterior lower wall (3. 1cm) of the external auditory canal is longer than the posterior upper wall (2.5cm).

The lateral13 of the external auditory canal is a cartilaginous external auditory canal based on the cartilage of the external auditory canal, and the medial 2/3 is a bony external auditory canal based on bones. The connection between them is very narrow; The stenosis is about 2cm away from the external auditory canal, and the narrowest part of the external auditory canal is called isthmus, which can prevent foreign bodies from entering the external auditory canal and invading the tympanic membrane. External auditory canal cartilage and auricle cartilage are continuous. When examining the tympanic membrane in clinic, lifting the auricle upward and backward can straighten the external auditory canal and facilitate observation.