1. Breathing or pulmonary airflow with the aid of oxygen from the atmospheric air is drawn internal and carbon dioxide-wealthy alveolar air is launched out.

2. Diffusion of each oxygen and carbon dioxide throughout the alveolar membrane.

3. Gases are transported at some stage in the frame cells with the aid of using the blood.

4. Diffusion of oxygen and carbon dioxide among blood and tissues of the frame.

5. The cells make use of oxygen for catabolic reactions, ensuing withinside the launch of carbon dioxide.