Which body system includes the alveoli and is primarily responsible for gas exchange?

• A. Respiratory System
• B. Digestive System
• C. Integumentary System
• D. Nervous System

Answer: (A)

Gas exchange happens where air meets blood in the lungs, specifically in the alveoli. These tiny sacs, wrapped in capillaries, provide a huge surface area and very thin barriers so oxygen can move into the bloodstream and carbon dioxide can be released from the blood to be exhaled. The system that includes the lungs and alveoli and handles this gas exchange is the respiratory system. The other systems don’t perform this function: the digestive system breaks down food and absorbs nutrients, the integumentary system protects the body and regulates temperature, and the nervous system controls and coordinates body activities.