Gas Exchange in the Respiratory System: How Oxygen and Carbon Dioxide Move

Gas exchange occurs in the respiratory system in the alveoli, which are tiny air sacs located at the end of the bronchioles. Oxygen from the air we breathe diffuses across the thin walls of the alveoli and into the surrounding capillaries, where it binds to hemoglobin in red blood cells for transport to the body's tissues. At the same time, carbon dioxide from the body's tissues diffuses into the capillaries and then into the alveoli, where it is exhaled out of the body. This process is facilitated by the large surface area of the alveoli and the thin walls that allow for efficient diffusion of gases.