What is the function of the epiglottis?

The function of the epiglottis is to prevent food and foreign matter from entering the trachea. The epiglottis is a flap of cartilage located at the root of the tongue. During swallowing, it automatically folds down to cover the trachea, thereby directing food and liquids into the esophagus and preventing aspiration into the respiratory tract. This action is crucial for protecting the airway from obstruction and ensuring that the swallowed substances go into the digestive tract rather than the lungs, which can lead to choking or aspiration pneumonia.

The other options provide functions related to different parts of the respiratory and digestive systems but do not accurately describe the role of the epiglottis. For instance, gas exchange in the alveoli is a function of the alveoli themselves, not the epiglottis. The expansion of the lungs during inhalation involves the diaphragm and intercostal muscles. Finally, while the larynx does connect to the trachea, the epiglottis specifically functions in protecting that airway rather than directly connecting structures.