Final answer:
A vertically lengthened pharynx during swallowing indicates a laryngeal change involving upward movement and protective mechanisms to prevent food from entering the respiratory tract.
Step-by-step explanation:
When the pharynx becomes vertically longer, this is indicative of a laryngeal change that occurs primarily during swallowing. The mechanism involves various structures: the soft palate, uvula, epiglottis, and larynx itself. During swallowing, the soft palate and uvula rise to close off the nasopharynx, while the larynx is pulled upwards, and the epiglottis folds down to cover the glottis. These actions prevent food from entering the respiratory tract. Additionally, the expansion of the pharynx accommodates the food bolus, which is then pushed into the esophagus as the elevator skeletal muscles of the pharynx contract and then relax while the constrictor muscles contract to initiate peristalsis.