What is the primary function of the respiratory system?

The primary function of the respiratory system is to obtain oxygen and remove carbon dioxide. This process is vital for sustaining life, as oxygen is required by the body's cells for energy production through cellular respiration. During respiration, oxygen is inhaled into the lungs, where it diffuses into the bloodstream and is transported to the cells. At the same time, carbon dioxide, which is a byproduct of cellular metabolism, is transported back to the lungs and expelled from the body when exhaling. This gas exchange is crucial for maintaining the pH balance in the body and ensuring that tissues receive the oxygen they need to function.

The other options represent functions of different systems or processes in the body. Transporting blood throughout the body is primarily the function of the circulatory system. Producing hormones is a key role of the endocrine system, and supporting the body's skeletal structure is the function of the skeletal system itself. Each of these systems contributes to the overall functioning of the body, but they do not encompass the core responsibility of the respiratory system, which centers on gas exchange.