ATI Pathophysiology Practice Exam

What structure in the respiratory system is responsible for gas exchange?

1. Bronchioles

2. Alveoli

3. Trachea

4. Larynx

The correct answer is: Alveoli

The alveoli are the key structures in the respiratory system responsible for gas exchange. These tiny, balloon-like sacs are located at the end of the bronchioles and provide a large surface area because they are often clustered together like grapes. This design maximizes contact with capillaries, which are small blood vessels that surround the alveoli. Gas exchange occurs due to diffusion, where oxygen from the air in the alveoli passes into the blood in the capillaries, and carbon dioxide from the blood is released into the alveoli to be exhaled. The thin walls of the alveoli—composed of a single layer of epithelial cells—further facilitate this efficient exchange. Therefore, their unique structure and location make the alveoli essential for the process that supplies oxygen to the body and removes carbon dioxide.