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How do the auditory tubes connect the nasopharynx to the middle ears?

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Illustration showing different animals and their respiratory organs: a spider with book lungs, a chicken with lungs, a sponge with labeled inflow and outflow pores, a fish with gills, and a caterpillar with spiracles. — Respiratory system Different methods of respiration in animals.

The eustachian tube, also known as the auditory tube, is a hollow structure measuring approximately 31–38 mm in length that serves as a vital connection between the middle ear and the nasopharynx.123

The tube extends downward and inward from the tympanic cavity (middle ear) to the nasopharynx, which is the space located behind the nasal passages and above the soft palate. Anatomically, the upper portion of the tube near the middle ear is narrow and surrounded by bone, while the section closer to the pharynx widens and becomes cartilaginous.12

The tube is lined with a mucous membrane continuous with that of the middle ear and is covered in cilia, which help drain secretions into the pharynx. While typically closed, the tube opens during swallowing to ventilate the middle ear and equalize air pressure on both sides of the tympanic membrane.12