What are the primary functions of the respiratory system?

The primary functions of the respiratory system center around the exchange of gases, specifically oxygen and carbon dioxide, between the lungs and the blood. This vital process occurs in the alveoli, which are tiny air sacs in the lungs where oxygen is absorbed into the bloodstream, and carbon dioxide is released from the blood into the lungs to be exhaled. This exchange is crucial for maintaining adequate oxygen levels in the body, which supports cellular respiration and energy production.

While the respiratory system does play a role in regulating pH and can have an indirect impact on body temperature through the process of panting or altering breathing rates, its primary function is not temperature regulation. Additionally, the supply of oxygen to the heart is a function that is facilitated by the circulatory system, utilizing the oxygen-rich blood delivered from the lungs. The transportation of nutrients in the blood is also a function of the circulatory system and not the respiratory system, as this involves the distribution of substances absorbed from the digestive tract.

Therefore, option B correctly identifies the fundamental role of the respiratory system in gas exchange, which is essential for life.