General information
The term “auditory canal” refers to two different anatomical structures. On the one hand, it refers to the “internal auditory canal” (Meatus acusticus internus), on the other hand to the “external auditory canal” (Meatus acusicus externus). Colloquially, however, the latter is usually meant.
The external auditory canal
The external auditory canal as part of the outer ear has a length of about 2 – 2.5 cm in humans and extends from the auricle to the eardrum, which separates it from the so-called middle ear. In the outer third of its course, its wall is formed by cartilage, while the remaining two thirds are bony and part of the temporal bone. It is completely lined by skin, which finally merges into the eardrum.
In addition to the skin, bristle hairs (tragi) in the outer third protect our auditory canal from foreign bodies. Special sebaceous glands, the ball glands, together with the secretion of the sebaceous glands and flaked skin scales form the earwax (cerumen). This wax also has a protective function by acting as an antibacterial and antifungal agent and thus counteracting infections.
In addition to its function of directing the sound bundled by the auricle to the eardrum, the external auditory canal is also capable of amplifying the sound through its own resonance. This happens mainly in the frequency range of 2000 – 4000 Hz, which is why we are more sensitive to these frequencies than to others. So it is not surprising that part of our main speech range (the frequency in which we speak, approx.
500 – 3000 Hz) lies within this range. Diseases of the auditory canal are often caused by the use of cotton swabs to clean it. One of the most common diseases caused by this is ear canal furuncle.
This is an inflammation of the hair follicles of the auditory canal caused by bacteria and is characterized by pain caused by pressure on the ear or by chewing. It is treated by alcohol-soaked strips and antibiotic-containing ointments which are inserted into the ear. When the doctor inserts a cotton swab or an otoscope, some people may experience a coughing sensation. This is due to the fact that the external auditory canal is innervated by a branch of the same nerve that sensitively innervates our larynx and is in no way a cause for concern.
