What is the main function of the respiratory system?

The primary function of the respiratory system is to deliver air to the lungs, where gas exchange occurs. This system plays a crucial role in bringing oxygen into the body and expelling carbon dioxide from it. When we inhale, air enters the nasal cavity or mouth, travels down the trachea, and reaches the lungs, specifically the alveoli, where oxygen diffuses into the bloodstream. This exchange is vital for maintaining cellular respiration, allowing cells to produce energy.

While the other options reflect important bodily functions—such as circulation, nutrient transport, and waste removal—these functions are primarily handled by other systems. The circulatory system is responsible for blood circulation, the digestive system transports and absorbs nutrients, and the excretory system handles waste products. Thus, delivering air to the lungs is distinctly the main function of the respiratory system, emphasizing its unique role in maintaining physiological homeostasis through gas exchange.