What is the primary function of the respiratory system?

The primary function of the respiratory system is to supply the body with oxygen and remove carbon dioxide. This process is essential for maintaining cellular respiration, which is how cells produce energy. When we inhale, oxygen enters the lungs and is transferred to the bloodstream, where it is then delivered to cells throughout the body. At the same time, carbon dioxide, a byproduct of cellular metabolism, is picked up by the blood and transported back to the lungs, where it is expelled from the body when we exhale. This exchange of gases—oxygen in and carbon dioxide out—is crucial for sustaining life and ensuring the body can function optimally.

Other options represent different body system functions. Circulating blood throughout the body is primarily the role of the cardiovascular system. Digesting food involves the digestive system, which breaks down food into nutrients for energy. Meanwhile, regulating body temperature is a function primarily associated with the integumentary system and, to some extent, the hypothalamus in the brain. Understanding the specific role of the respiratory system is key for recognizing how vital it is to our overall health and well-being.