What is the primary function of the respiratory system?

The primary function of the respiratory system is oxygen exchange, which is crucial for maintaining the body’s metabolism and overall homeostasis. This system facilitates the inhalation of oxygen from the atmosphere into the lungs, where it then diffuses into the bloodstream. Simultaneously, carbon dioxide, a waste product of metabolism, is expelled from the blood into the lungs and exhaled. This exchange process is vital because all cells in the body require oxygen to produce energy through cellular respiration, while the removal of carbon dioxide helps regulate blood pH and maintain appropriate gas concentrations in the body.

The other options pertain to different bodily functions: digestion refers to the breakdown of food for nutrient absorption, circulation involves the movement of blood throughout the body, and excretion deals with the removal of waste products from metabolism. While these systems are interconnected, they do not define the primary role of the respiratory system, which is centered on facilitating the vital exchange of gases.