The primary function of the lungs in humans is to facilitate the exchange of gases, specifically oxygen and carbon dioxide. When we breathe in, oxygen from the air enters the lungs and is transferred into the bloodstream through tiny air sacs called alveoli. Simultaneously, carbon dioxide, a waste product of metabolism, is expelled from the blood into the alveoli and then exhaled out of the body. This gas exchange is crucial for maintaining the body's oxygen levels and ensuring that cells receive the oxygen they need to produce energy.