Which system is responsible for taking in oxygen and releasing carbon dioxide?

The respiratory system is responsible for taking in oxygen and releasing carbon dioxide, a process known as gas exchange. When we inhale, oxygen from the air enters the lungs and diffuses into the bloodstream, where it is transported to cells throughout the body. At the same time, carbon dioxide, which is a waste product of cellular respiration, moves from the blood into the lungs and is expelled from the body when we exhale. This exchange of gases is crucial for maintaining the body's oxygen levels and removing carbon dioxide, thereby supporting cellular functions and overall metabolism.

In contrast, the digestive system is involved in breaking down food and absorbing nutrients, but it does not directly manage gas exchange. The excretory system focuses on removing waste products from the body, particularly in the form of urine, and is not responsible for the exchange of gases. Lastly, while the circulatory system plays an essential role in transporting gases like oxygen and carbon dioxide throughout the body, it does not itself perform the act of gas exchange; that is the function of the respiratory system.