Eustachian tubes, which are also sometimes known as the auditory or pharyngotympanic tubes, are small cartilage and bone canals. The canals connect the middle ear, which is an air-filled cavity in the internal structure of the ear, and the nasopharynx, the lower nasal cavity behind the mouth. This connection allows air movement into and out of the ear, maintaining the pressure inside the ear canal at the external atmospheric pressure.
Ear Pressure and Hearing
The function of the ear is to hear by converting sound waves to electrical impulses. Sound waves travel through the air and into the ear canal, where they proceed through the middle ear to vibrate the eardrum on the far end. The sound waves are then transmitted to the bones and structures of the inner ear, which are then responsible for transmitting the signals to the brain. Maintaining atmospheric pressure within the middle ear allows the sound waves to proceed unchanged.
Eustachian Tubes and Altitude
When the atmospheric pressure changes, there is sometimes a sensation in the ear as the pressure within the Eustachian tubes adjusts. When driving up a mountain or flying in an airplane, a popping sensation is often felt, hearing is impaired for a short period of time, or a popping sound is heard as the pressure adjusts. Swallowing, chewing, or yawning pulls on the neck muscles and can help the Eustachian tubes open, releasing the pressure in the ears.
Ear Drainage and the Nasal Cavity
The Eustachian tubes also allow mucus produced by the lining of the middle ear to drain. The mucus drains from the ear to the nasopharynx and then to the stomach, similar to the sinuses. The mucus is present to protect the ear from foreign material, similar to mucus in the nose and throat. Drainage prevents the ear from becoming clogged with this helpful material, which can affect hearing and increase the risk of ear infections.
In the case of respiratory illness, material can make its way from the nasal cavity to the ear through the auditory tubes. Blockage of the tube or tubes from a throat infection can result in an ear ache and potential spread of the infection to the inner ear.
Eustachian Tube Problems in Children
Children often have a more horizontally placed tube and may experience blocked drainage due to the anatomic position, resulting in a greater occurrence of ear infections. Doctors sometimes insert synthetic tubes to help keep the auditory tubes open and facilitate appropriate air and fluid exchange.
What Eustachian Tubes Do Not Do
The Eustachian tubes do not maintain balance per se; this is accomplished by hair cells in the inner ear. The pressure in the ear, though, can affect the function of the ear structures, so the auditory tubes play a role in maintaining the integrity of the system that maintains balance. Ear infections are known to affect equilibrium because of their clogging effect in the ear.
Similarly, swimmer’s ear is mistakenly attributed to problems with the Eustachian tubes. Water can become trapped in the ear canal and lead to an ear ache and dulled hearing, followed by inflammation and infection. The blockage prevents proper air movement to the ear drum, but is not a clogging of the auditory tubes.