What is the main purpose of the respiratory system?

The primary function of the respiratory system is to facilitate the exchange of gases, specifically oxygen and carbon dioxide, between the body and the environment. This process occurs in the lungs, where oxygen from the air is absorbed into the bloodstream and carbon dioxide, a waste product of metabolism, is expelled from the body. This gas exchange is vital for maintaining life, as oxygen is essential for cellular respiration— a process that generates energy for the body's cells. Additionally, the respiratory system plays a critical role in regulating blood pH by controlling the levels of carbon dioxide in the blood, further highlighting its importance in maintaining homeostasis in the body.

The other functions mentioned, such as circulating blood, controlling body temperature, and processing nutrients, are primarily associated with other body systems, like the circulatory system, integumentary system, and digestive system, respectively. Thus, the respiratory system's focus on gas exchange establishes its unique and crucial role in overall bodily function and health.