Where does the respiratory zone of the lungs begin?

• A. At the alveolar ducts
• B. At the terminal bronchioles
• C. At the respiratory bronchioles
• D. At the trachea

Answer: (C)

Verified step by step guidance

1. Understand the structure of the respiratory system: The respiratory system is divided into the conducting zone and the respiratory zone. The conducting zone includes structures that transport air to the lungs, while the respiratory zone is where gas exchange occurs.
2. Identify the components of the conducting zone: The conducting zone consists of the trachea, bronchi, bronchioles, and terminal bronchioles. These structures are primarily involved in the movement of air and do not participate in gas exchange.
3. Recognize the beginning of the respiratory zone: The respiratory zone starts at the respiratory bronchioles. These are the first structures where gas exchange begins, as they contain alveoli, which are tiny air sacs where oxygen and carbon dioxide are exchanged.
4. Differentiate between terminal bronchioles and respiratory bronchioles: Terminal bronchioles are the last part of the conducting zone and do not have alveoli. Respiratory bronchioles, on the other hand, are part of the respiratory zone and have alveoli, making them the starting point for gas exchange.
5. Conclude the location of the respiratory zone: Based on the structure and function of the respiratory system, the respiratory zone begins at the respiratory bronchioles, where the presence of alveoli allows for gas exchange.