Adolescent respiratory system and cardiovascular system. According to Sohu's query. Com, the respiratory tract of teenagers is different from that of adults. Teenagers' respiratory tract is relatively narrow, and respiratory tract mucus secretion is insufficient, which is easy to cause respiratory tract infection and injury. Teenagers breathe fast in a quiet state, but their vital capacity is far less than that of adults. In adolescence, their myocardial contractility is insufficient, their heart rate is fast and their contraction is low, their heart valves are not fully developed, and their heart volume and capacity are far less than those of adults. Teenagers mainly rely on accelerating breathing rhythm and raising heart rate to expand lung ventilation and heart input.