What shuts off the passage to the trachea and lungs?

The passage to the trachea and lungs is shut off by the epiglottis, a flap of cartilage located at the base of the tongue. During swallowing, the epiglottis folds down to cover the trachea, preventing food and liquids from entering the airway and directing them into the esophagus instead. This mechanism helps to protect the respiratory tract from aspiration and ensures that only air enters the lungs.