Which of the following is NOT a function of the respiratory system?

The respiratory system primarily functions to facilitate the intake of oxygen and the expulsion of carbon dioxide, a process known as gas exchange. This vital function occurs in the alveoli of the lungs, where oxygen from inhaled air diffuses into the bloodstream, while carbon dioxide, a waste product of metabolism, is removed from the blood and exhaled. Additionally, the respiratory system plays a role in maintaining the pH balance of blood by regulating carbon dioxide levels, which directly influence acid-base balance.

In this context, nutrient distribution is not a function attributed to the respiratory system; rather, it is primarily the role of the circulatory system. Nutrients derived from digested food are absorbed into the bloodstream via the digestive system and then transported to various tissues and organs throughout the body by the circulatory system. This clearly delineates the distinct functions of these systems, underscoring why nutrient distribution is not associated with the respiratory system.