The flap that prevents food from entering the trachea is the epiglottis. This leaf-shaped structure sits at the entrance to the larynx and helps direct swallowed material toward the esophagus instead of the windpipe.
During normal breathing, the epiglottis remains positioned to allow air to pass into the larynx and trachea. When swallowing begins, the larynx moves upward and forward, while the tongue and surrounding muscles help fold the epiglottis backward over the airway entrance. Food and liquid are then guided into the esophagus, the tube leading to the stomach. The movement is coordinated with brief closure of the vocal folds and a pause in breathing.
The epiglottis is made of elastic cartilage rather than bone, so it can bend and return to its usual shape. A common misconception is that it acts like a simple lid that independently snaps shut; swallowing involves several coordinated structures. The glottis is the opening between the vocal folds, the pharynx is the throat behind the mouth and nose, and the uvula hangs from the soft palate. If material enters the airway, the resulting aspiration can trigger coughing or, in serious cases, pneumonia.