What is the primary function of the respiratory system?

The primary function of the respiratory system is to facilitate the exchange of gases between the body and the environment. This involves inhaling oxygen from the air, which is critical for cellular respiration, a process that produces energy for the body's cells. During this process, carbon dioxide, a waste product of metabolism, is expelled when exhaling. This exchange occurs primarily in the lungs, where oxygen diffuses into the blood, and carbon dioxide is released from the blood into the air sacs (alveoli) of the lungs.

In contrast, the other options highlight functions of different bodily systems. Blood circulation is primarily managed by the cardiovascular system, which is responsible for transporting nutrients, gases, and hormones throughout the body. Digestion is a function of the digestive system, which breaks down food into nutrients for absorption. Hormone production is associated with the endocrine system, which regulates various bodily functions through chemical messengers. Understanding these distinctions underscores how the respiratory system's unique role is critical for maintaining the body's oxygen supply and removing carbon dioxide.