What part of the respiratory system is primarily involved in the exchange of oxygen and carbon dioxide?

The alveoli are the primary sites for the exchange of oxygen and carbon dioxide in the respiratory system. These tiny, balloon-like structures are located at the end of the bronchioles and provide an extensive surface area that is crucial for gas exchange. The walls of the alveoli are extremely thin and are surrounded by capillaries, which allows for efficient diffusion of gases. Oxygen from the inhaled air passes through the alveolar walls into the bloodstream, while carbon dioxide from the blood diffuses into the alveoli to be exhaled.

In contrast, the bronchi serve as passageways for air to travel to and from the lungs but are not involved in gas exchange themselves. The trachea is simply the airway that connects the throat to the bronchi, also playing no direct role in the exchange process. The diaphragm is a muscle that facilitates breathing by contracting and relaxing to change the volume of the thoracic cavity, but it does not participate directly in the exchange of gases.