Final answer:
The epiglottis is the cartilaginous flap that prevents food and liquid from entering the trachea during swallowing by covering the glottis and ensuring that ingested material is directed into the esophagus.
Step-by-step explanation:
The leaf-shaped flap of cartilage that prevents food and liquid from entering the trachea during swallowing is called the epiglottis. The epiglottis is a flexible piece of elastic cartilage located at the superior part of the larynx. During swallowing, the larynx is pulled upwards and the epiglottis folds down to cover the glottis, thus blocking access to the trachea. This mechanical action ensures that food and liquids are directed into the esophagus rather than the respiratory tract.
Figure 22.7 in the Larynx shows how the epiglottis, attached to the thyroid cartilage, upon folding, rests on the glottis. As a consequence of this arrangement, when food is swallowed incorrectly and enters the trachea, a cough reflex is triggered to expel the food from the respiratory pathway. This reflex is a vital protective mechanism that prevents aspiration and potential respiratory complications.