What closes and seals off the lower airway during swallowing?

The epiglottis plays a crucial role in protecting the airway during swallowing. When food or liquid is ingested, the epiglottis folds down over the larynx, which prevents aspiration (the inhalation of food or liquid) into the trachea and lungs. This structure ensures that the lower airway is sealed off, directing the swallowed materials into the esophagus instead.

The trachea is the passageway for air to the lungs but does not actively seal off or close during swallowing. The larynx, while involved in vocalization and protecting the airway, does not directly cover the airway in the same way the epiglottis does during swallowing. The esophagus is the tube that carries food to the stomach but does not have a role in sealing the airway. Thus, the epiglottis is the critical anatomical structure responsible for this protective mechanism during the swallowing process.