What function does the respiratory system primarily serve?

The primary function of the respiratory system is to facilitate gas exchange of oxygen and carbon dioxide. This process occurs in the lungs, where oxygen from the inhaled air diffuses into the bloodstream, allowing it to be transported to the body's tissues, while carbon dioxide, a waste product of cellular metabolism, diffuses from the blood into the alveoli of the lungs to be exhaled. The efficiency of this gas exchange is crucial for maintaining cellular respiration, which is the process by which cells produce energy.

While the other options involve important bodily functions, they do not represent the primary role of the respiratory system. The transportation of nutrients to cells is primarily a function of the circulatory system. Similarly, regulating body temperature is largely managed by the integumentary and circulatory systems, not the respiratory system. Protecting the body from pathogens is a function associated with the immune system, although the respiratory system does have some protective mechanisms, such as mucus production and cilia, its main role remains focused on gas exchange.