Which body system is involved in gas exchange?

• A. Circulatory System
• B. Muscular System
• C. Respiratory System
• D. Endocrine System

Answer: (C)

The respiratory system is primarily responsible for gas exchange in the body. Its main function is to take in oxygen from the atmosphere and expel carbon dioxide as a waste product. This process occurs mainly in the alveoli, tiny air sacs in the lungs where the exchange of gases takes place. Oxygen from the inhaled air diffuses across the alveolar membrane into the blood in the surrounding capillaries, while carbon dioxide in the blood moves into the alveoli to be exhaled.

While the circulatory system plays a crucial role in transporting the oxygenated blood from the lungs to the body's tissues and returning deoxygenated blood back to the lungs, it does not participate in the actual process of gas exchange. The muscular system is responsible for movement and does not directly facilitate gas exchange. Similarly, the endocrine system deals with hormone regulation and communication within the body, which is unrelated to the respiratory process of exchanging gases. Therefore, the respiratory system is the main body system involved in the act of gas exchange.