In the conducting zone, which of the following occurs?

• A. Gas exchange
• B. Heating and humidifying air
• C. Filtration of blood
• D. Immune response activation

Answer: (B)

The conducting zone of the respiratory system is primarily responsible for the passage of air from the external environment to the lungs. One of its main functions is to prepare the air for optimal gas exchange in the alveoli, which occurs in the respiratory zone. This preparation involves several processes, notably heating and humidifying the inspired air.

As air travels through the nasal passages and into the trachea and bronchi, it encounters mucous membranes that are rich in blood vessels. These structures warm the air to body temperature and add moisture, which is essential for maintaining the health of the delicate lung tissues. Proper humidity helps to prevent irritation and damage to the respiratory epithelium, ensuring that the airways remain wet and functional for effective gas exchange in the lower respiratory regions.

The other choices do not align with the primary functions of the conducting zone. Gas exchange specifically occurs in the alveolar sacs of the respiratory zone, not the conducting zone. While some aspects of the immune response may involve structures within the respiratory tract, such as mucus and cilia, the primary role of the conducting zone is not immune activation, but rather facilitating air passage. Additionally, filtration of blood is not a function of the respiratory system; instead, the kidneys are responsible for filtering blood