The auditory canal is a tube that connects the pinna, or fleshy outer visible part of the ear, and the tympanic membrane, or eardrum. Together, the pinna and the auditory canal make up the external ear and measure about 1 inch (26 mm) long. The ear canal has two primary functions: helping the auditory process by funneling sound toward the eardrum and protecting the eardrum from injury.
The inner two-thirds of the auditory canal are bony and free of hair and glands. In the cartilaginous outer third of the outer canal, tiny hairs grow perpendicular to the canal wall and help clean the canal. Sebaceous glands produce sebum, an oily substance made up of fats. Cerumenous glands produce cerumen, or earwax, which helps to lubricate the canal and keeps it waterproof. Too much earwax can be a problem when it impacts and causes temporary hearing loss, requiring removal by a doctor.
The ear canal is responsible for amplifying sound and directing it toward the eardrum. From the pinna to the tympanic membrane, sound is increased by 5 to 15 decibels (dB) in the 2,000 to 4,000 Hertz (Hz) range due to the resonance of the auditory canal. The human ear is most sensitive to sound within this range and most vulnerable to damage from noises that are too loud.
Since the auditory canal is so close to the outside of the body, it is susceptible to many disorders, infections, and injuries. Although the depth and curvature of the ear canal provides some protection from injury, they still may occur or objects may become stuck in the ear. Also, the ear is a warm, moist organ and can be an ideal environment for fungal infections to grow. Bacterial infections like otitis externa, also known as swimmer’s ear, can infect the external ear, and may damage the eardrum if not treated.
Cleaning the ear canal is almost never necessary and may be dangerous. The auditory canal is a self-cleansing organ, so external cleansing may interfere with this process. Objects, like cotton swabs, inserted into the ear can damage or even puncture the eardrum.
The auditory canal, like the nail bed, is host to a process called epithelial migration. Skin cells move from the tympanic membrane toward the pinna, helping clean the ear and move foreign objects, earwax, and shed hairs toward the pinna. Some researchers believe that the process is aided by chewing motions, which stretch and shift the ear canal and may help the cells migrate.