What structure prevents food and liquid from entering the trachea during swallowing?

The correct answer is the epiglottis, as this structure plays a crucial role in the process of swallowing. During swallowing, the epiglottis folds down over the larynx, effectively sealing off the entrance to the trachea. This action prevents food and liquids from entering the airway, thereby protecting the lungs from aspiration and potential respiratory complications.

The larynx is primarily involved in producing sound and protecting the airway during breathing, but it does not directly prevent substances from entering the trachea during swallowing. The cricoid cartilage serves as a supportive structure to the larynx and helps maintain the airway but does not have a role in preventing food from entering the trachea. The diaphragm is a muscle involved in the respiratory process, aiding in inhalation and exhalation, but it does not interact with the swallowing process or prevent aspiration.