Question

Which of the following are parts of the exchange zone?
I) Alveolar atria
II) Alveoli
III) Terminal bronchiole
IV) Respiratory bronchiole
V) Tertiary bronchi

• A. II only
• B. II, III, IV, and V only
• C. I, II, and III only
• D. I, II, and IV only

Answer 1

The correct option is D I, II, and IV only

The human respiratory system has two zones- the conducting zone and the exchange zone. The conducting zone is responsible for the transportation of atmospheric air into the exchange zone, filtering the air from foreign particles along with humidifying it and bringing it to body temperature. The exchange zone is the site of gaseous exchange between blood and the atmospheric air. The conducting zone starts from the external nostrils and ends up at the bronchial tree. In the bronchial tree, the trachea bifurcates into two primary bronchi which further divides into several secondary bronchi and further subdivide into tertiary bronchi. The tertiary bronchi divides into the terminal bronchiole as a result of further subdivision. The terminal bronchiole forms the respiratory bronchiole which is a part of the respiratory tree. The respiratory tree is also called the exchange zone. It starts with respiratory bronchiole that further subdivide into alveolar ducts which in turn terminate into expanded passages known as alveolar atria. These atria divides into alveolar sacs or air sacs which further opens into the alveoli or acini. It is through the alveoli that the gaseous exchange takes place through simple diffusion.