Which organ system is primarily involved in gas exchange and includes the lungs?

• A. Renal
• B. Digestive
• C. Pulmonary
• D. Integumentary

Answer: (C)

Gas exchange happens mainly in the lungs, where oxygen from the air diffuses into the blood and carbon dioxide diffuses out to be exhaled. This function is carried by the pulmonary system, which includes the lungs, airways, alveoli, and the muscles that drive breathing. The lungs provide a large surface area and the thin alveolar walls needed for efficient diffusion between air and blood. Other organ systems don’t handle the primary gas-exchange task—kidneys (renal) manage waste and fluid balance, the digestive system processes nutrients, and the skin (integumentary) isn’t the main route for gas exchange in humans.