Which system provides exchange of oxygen and carbon dioxide to feed cells and tissues?

• A. Respiratory System
• B. Endocrine System
• C. Reproductive System
• D. Nervous System

Answer: (A)

Gas exchange to supply cells with oxygen and remove carbon dioxide is done by the respiratory system. In the lungs, tiny air sacs called alveoli sit close to capillaries. Oxygen from inhaled air diffuses across the alveolar wall into the blood and binds to hemoglobin to be carried to tissues. Carbon dioxide, a waste product from cells, diffuses from the blood into the alveoli to be exhaled. This exchange happens because of the different partial pressures of the gases. Other systems regulate body processes—hormone signals, reproduction, and rapid communication—but they do not perform the actual gas exchange needed to feed tissues.