so called for Italian physician Bartolomeo Eustachio (d.1574), who discovered the passages from the ears to the throat. His name is from Latin Eustachius (see Eustace).
eustachian tube n.
A slender tube that connects the tympanic cavity with the nasal part of the pharynx and serves to equalize air pressure on either side of the eardrum. Also called auditory tube, salpinx.
A tube made up of bone and cartilage that connects the middle ear to the back of the mouth.
Note: Swallowing during airplane takeoffs and landings allows air to move through the Eustachian tube to equalize pressure across the eardrum, causing the ears to “pop.”