Final answer:
The nasopharynx is lined with pseudostratified ciliated columnar epithelium, suited for its role in respiration and speech, whereas the oropharynx has a stratified squamous epithelium to protect against abrasion from food and also contains lymphoid tissue in the form of tonsils for immune defense.
Step-by-step explanation:
The lining of the oropharynx and that of the nasopharynx differ in their epithelial structure due to their different functions in the respiratory and digestive systems. The nasopharynx, primarily involved in breathing and speech, is lined with pseudostratified ciliated columnar epithelium which helps trap and move particles out of the airway. Conversely, the oropharynx, which is a passageway for both food and air, changes to a stratified squamous epithelium as it must withstand the abrasion from swallowed food and fluids. In the oropharynx, the presence of lymphoid tissue in the form of palatine and lingual tonsils plays a crucial role in the immune defense by trapping and destroying pathogens.