Final answer:
The epiglottis is the structure that functions as a lid over the entrance to the laryngopharynx, preventing food and beverages from entering the trachea during swallowing.
Step-by-step explanation:
The structure that acts as a lid over the entrance to the laryngopharynx is the epiglottis.
Attached to the thyroid cartilage, the epiglottis is a flexible piece of elastic cartilage that covers the opening of the trachea. During the process of swallowing, it swings downward to close off the glottis, which is the part that includes the vestibular folds (false vocal cords), the true vocal cords, and the space between these folds. This action prevents food and beverages from entering the trachea and ensures that they pass into the esophagus instead.
When food or liquid is inadvertently aspirated into the trachea, a strong cough reflex is triggered. This reflex is aimed at expelling such material from the larynx back into the pharynx and thus protecting the lower respiratory tract from aspiration.