What physiological process primarily takes place in the lungs?

The primary physiological process that occurs in the lungs is gas exchange. This process involves the transfer of oxygen from the air into the bloodstream and the removal of carbon dioxide from the blood to be exhaled. Within the alveoli, the tiny air sacs in the lungs, oxygen molecules diffuse across the alveolar membrane into the blood, while carbon dioxide diffuses in the opposite direction to be expelled from the body.

The lungs are specifically adapted for this function, with a large surface area provided by millions of alveoli, thin walls that facilitate swift diffusion, and a rich supply of capillaries for efficient transport of gases. This vital process supports cellular respiration, where oxygen is utilized by cells for energy production, and plays a critical role in maintaining acid-base balance in the body by regulating carbon dioxide levels.