Final answer:
The epiglottis is a flap that covers the glottis to prevent food from entering the larynx and trachea during swallowing.
Step-by-step explanation:
The flap that prevents food from passing the glottis and entering the larynx is called the epiglottis. During swallowing, the epiglottis folds inferiorly to cover the opening to the larynx. This action blocks the passage to the trachea and bronchi, directing food and beverages into the esophagus instead. The larynx is pulled upward, and the soft palate and uvula rise to close off the entrance to the nasopharynx. These synchronized movements are critical to preventing aspiration of food into the respiratory tract.