What structure prevents food from entering the trachea during swallowing?

The structure that prevents food from entering the trachea during swallowing is the epiglottis. This flexible flap of cartilage is located at the base of the tongue and folds over the trachea when swallowing occurs. By doing so, it acts as a protective barrier, directing food and liquids into the esophagus and away from the airway. This function is crucial for safe swallowing, as it helps prevent choking and ensures that air passage remains unobstructed during the intake of food.

In contrast, the esophagus is the muscular tube that connects the throat (pharynx) with the stomach but does not play a role in preventing food from entering the trachea. The pharynx serves as a passage for both air and food but does not have the specific mechanism to close off the airway like the epiglottis does. Alveoli, on the other hand, are tiny air sacs in the lungs involved in gas exchange, and they do not have any direct role in the swallowing process. The distinct function of the epiglottis in closing off the trachea is essential for the protection of the respiratory system while allowing for the safe passage of food and liquid.