1. Inhalation: When we breathe in, air enters our lungs through our nose or mouth and travels down the windpipe (trachea) into the smaller branches called bronchi. These bronchi further divide into even smaller tubes called bronchioles.
2. Alveoli: The bronchioles end in clusters of tiny air sacs called alveoli. The alveoli are where the actual gas exchange occurs. They have thin walls that are covered in capillaries, which are tiny blood vessels.
3. Diffusion of Carbon Dioxide: Carbon dioxide is a waste gas produced by cells during metabolism. It is carried by the blood from the tissues to the lungs. When the blood reaches the alveoli, carbon dioxide diffuses out of the capillaries into the alveoli. This process is driven by the concentration gradient, with higher carbon dioxide levels in the capillaries and lower levels in the alveoli.
4. Diffusion of Oxygen: At the same time, oxygen from the inhaled air diffuses across the thin walls of the alveoli into the capillaries. This process is also driven by the concentration gradient, with higher oxygen levels in the alveoli and lower levels in the capillaries.
5. Oxygenated Blood: The oxygen-rich blood in the capillaries is then carried away by the pulmonary veins back to the heart and then pumped throughout the body, supplying oxygen to the cells.
6. Exhalation: Once the gas exchange is complete, we breathe out, expelling the carbon dioxide-rich air from the lungs.
This continuous process of gas exchange in the alveoli ensures that the body receives a fresh supply of oxygen and releases carbon dioxide, which is a waste product of cellular respiration.
