Final answer:
The alveoli are the primary structures of the respiratory system associated with gas exchange, which is the essence of respiration. Other parts of the system, such as the trachea and bronchi, serve as air passageways and are part of the conducting zone.
Step-by-step explanation:
The structures of the respiratory system most associated with the function of respiration are the alveoli.
The process of respiration primarily involves the exchange of gases - oxygen and carbon dioxide. This gas exchange occurs in the respiratory zone, particularly in the alveoli of the lungs. The alveoli are tiny air sacs surrounded by capillaries where oxygen enters the blood and carbon dioxide is removed. Other components of the respiratory system such as the trachea, bronchi, and nose, fall under the conducting zone, which serves to warm, humidify, and transport air to the alveoli but is not directly involved in the process of gas exchange.
Additionally, the respiratory system needs the cardiovascular system to transport the oxygen and carbon dioxide to and from the alveoli, as the cardiac circulation provides the network of blood vessels that facilitate this exchange. The pharynx, interestingly, plays a role in both the digestive and respiratory systems, as it facilitates the passage of both air and food.