Nerve06/eyes and ears/pharyngotympanic (Eustachian) tube

The pharyngotympanic (Eustachian) tube is connected to the pharynx and is usually closed, making the tympanic cavity a closed space. During swallowing or yawning, the tube is opened and the cavity becomes open to the outside, making the pressure inside the cavity equal to that of the atmosphere.

At the first floor of a building, the pressure of the cavity is equal to the atmospheric pressure at that level (shown in dark blue). Both the tube and cavity are closed.

The atmospheric pressure is lowered (shown in light blue) as an airplane or an elevator of a high building goes up. Since the tympanic cavity is a closed space, the pressure inside does not change from the 1st floor level (shown in dark blue). This results in pressure difference on the two sides of the tympanic membrane, which becomes curved. Since the tympanic membrane also has sensory nerves, the curve causes an uncomfortable or painful sensation making the subject want to 'pop' his ears.

At this time, swallowing would cause the tube to open, releasing the high pressure to the pharynx.

This cancels the pressure difference on the two sides, and the curving, of the tympanic membrane. The ears are 'popped', and the uncomfortable sensation disappears.

Challenge Quiz

1.

The pharyngotympanic (Eustachian) tube is opened closed  正解! during swallowing.