Which system is primarily responsible for gas exchange in the body?

The respiratory system is primarily responsible for gas exchange in the body because it includes the structures and processes necessary for bringing oxygen into the body and expelling carbon dioxide. This system consists of the lungs, trachea, bronchi, and alveoli, where the actual exchange of gases occurs.

When we inhale, oxygen enters the lungs and reaches the alveoli, tiny air sacs where oxygen diffuses into the blood, and at the same time, carbon dioxide from the blood passes into the alveoli to be expelled when we exhale. This vital function of the respiratory system is crucial for maintaining the body's oxygen levels and eliminating carbon dioxide, which is a byproduct of metabolism.

In contrast, the circulatory system transports oxygen-rich blood from the lungs to the rest of the body and brings carbon dioxide back to the lungs, but it does not perform the gas exchange itself. The nervous system controls and regulates bodily functions, including breathing, but does not directly participate in gas exchange. The digestive system is responsible for breaking down food and absorbing nutrients, which is unrelated to the gas exchange process. Thus, the respiratory system is integral to achieving the essential function of gas exchange.