What is the primary function of the respiratory system?

The primary function of the respiratory system is to facilitate gas exchange between oxygen and carbon dioxide. This system is essential for supplying the body with oxygen, which is necessary for cellular metabolism and energy production. During respiration, oxygen is inhaled into the lungs, where it diffuses across the alveolar membranes into the bloodstream. Simultaneously, carbon dioxide, which is a waste product of metabolism, diffuses from the blood into the alveoli to be exhaled. This process not only maintains the oxygen levels necessary for bodily functions but also helps regulate the acidity of blood by controlling levels of carbon dioxide.

In contrast, other systems listed in the choices perform entirely different roles. For instance, the circulatory system is responsible for transporting blood and nutrients, while the digestive system breaks down food for energy. The regulation of body temperature is largely managed by the integumentary system, rather than the respiratory system. Understanding these distinct functions helps clarify the vital role of the respiratory system in maintaining homeostasis and supporting life.