What physiological process occurs at the alveoli?

The physiological process that occurs at the alveoli is gas exchange with blood. The alveoli are tiny air sacs located in the lungs where oxygen from the inspired air diffuses into the blood and carbon dioxide from the blood is expelled into the alveoli to be exhaled. This exchange is facilitated by the thin walls of the alveoli, which allow for efficient transfer of gases between the air and the bloodstream. Oxygen diffuses from the alveolar air into the pulmonary capillaries, where it binds to hemoglobin in red blood cells, while carbon dioxide moves in the opposite direction to be removed from the body. This fundamental process is essential for maintaining adequate oxygen levels in the blood and removing waste gases, thus supporting cellular respiration throughout the body.