What is the primary function of the respiratory system?

What is the primary function of the respiratory system?

• A. Pumping blood through the body
• B. Exchange of oxygen and carbon dioxide between the body and environment
• C. Filtering and digesting foods
• D. Regulating hormones

Answer: (B)

The primary function of the respiratory system is to exchange gases between the air and the bloodstream. Oxygen from inhaled air diffuses across the thin walls of the alveoli into the blood, where it binds to hemoglobin and is carried to tissues throughout the body. Carbon dioxide, a waste product of metabolism, moves from the blood into the alveoli to be exhaled. This gas exchange relies on a large surface area and a thin, moist barrier between air and blood, driven by differences in gas partial pressures. The respiratory system also helps regulate the body's acid-base balance by adjusting CO2 levels, which influence blood pH. Other options describe functions of different systems: pumping blood is the job of the cardiovascular system; filtering and digesting foods belong to the digestive system; regulating hormones is the endocrine system. The gas-exchange role is what uniquely defines the respiratory system.

The primary function of the respiratory system is to exchange gases between the air and the bloodstream. Oxygen from inhaled air diffuses across the thin walls of the alveoli into the blood, where it binds to hemoglobin and is carried to tissues throughout the body. Carbon dioxide, a waste product of metabolism, moves from the blood into the alveoli to be exhaled. This gas exchange relies on a large surface area and a thin, moist barrier between air and blood, driven by differences in gas partial pressures. The respiratory system also helps regulate the body's acid-base balance by adjusting CO2 levels, which influence blood pH.

Other options describe functions of different systems: pumping blood is the job of the cardiovascular system; filtering and digesting foods belong to the digestive system; regulating hormones is the endocrine system. The gas-exchange role is what uniquely defines the respiratory system.