MEDICAL ANIMATION TRANSCRIPT: The upper respiratory tract consists of the nose, mouth, pharynx, and larynx. As air passes through them, these structures provide physical and immunologic barriers to infectious pathogens and other debris. In the nose, viruses, bacteria, and other debris stick to the mucus in the nasal passageway, while the nasal mucosa, warms and humidifies the air. The shape of the pharynx forces air to take a 90-degree turn downward. Larger airborne particles can't make the turn, so they get caught in the mucosa of the posterior wall instead. The palatine and pharyngeal tonsil contain immune cells that engulf and destroy pathogens that land on them. Air then passes through the larynx on its way to the lower respiratory tract. The common cold, also known as nasopharyngitis or acute rhinitis is the most common viral upper respiratory tract infection. Cold viruses, most commonly the rhinovirus, enter the body when contaminated hands touch the nose or mouth, or when viru...