The main purpose of the human respiratory system is to facilitate gas exchange between the body and the environment. This system allows for the intake of oxygen from the air, essential for cellular respiration, and the expulsion of carbon dioxide, a waste product of metabolism. Air enters the body through the nose or mouth, travels down the trachea, and into the lungs, where it reaches the alveoli—tiny air sacs where gas exchange occurs. The oxygen diffuses into the bloodstream, and carbon dioxide is expelled when we exhale. This process is crucial for maintaining the body's energy levels and overall health.