Final answer:
Gas exchange in the lungs is facilitated by diffusion primarily in the alveoli, where oxygen and carbon dioxide are exchanged between the air and the bloodstream. A large surface area and the matching of ventilation and perfusion are critical for efficient gas exchange.
Step-by-step explanation:
Gas exchange in the lungs is facilitated by a process known as diffusion. This occurs primarily in the alveoli, which are lined with capillaries and ensure the efficient transfer of gases. The alveoli provide a large surface area (approximately 75 m² in humans due to the presence of around 300 million alveoli) that maximizes gas diffusion. Oxygen diffuses from the alveoli into the blood because the concentration of oxygen in the inhaled air is higher than in the oxygen-depleted blood. Conversely, carbon dioxide diffuses from the blood into the alveoli since its concentration is higher in the blood than in the exhaled air. This movement is driven by the different concentrations of gases, utilizing the basic principles of diffusion.
The process of ventilation, the movement of air into and out of the lungs, and perfusion, the flow of blood in the pulmonary capillaries, are also essential for efficient gas exchange. These two processes must be well-matched for optimal gas transfer. Any imbalance due to factors such as blocked airways or disease can impact the effectiveness of gas exchange.