Final answer:
The Eustachian tube connects the middle ear to the pharynx and helps equalize the pressure between the two. When you swallow or yawn, the Eustachian tube opens to allow air to flow in or out of the middle ear.
Step-by-step explanation:
The Eustachian tube, also known as the auditory tube or pharyngotympanic tube, connects the middle ear to the pharynx (throat). This tube helps equalize the pressure between the middle ear and the outside environment. When you swallow or yawn, the muscles in the pharynx contract, allowing the Eustachian tube to open and air to flow in or out of the middle ear.