What are the primary functions of the respiratory system?

• A. Gas exchange
• B. Breathing
• C. Inhalation and exhalation
• D. Filtering of air

Answer: (C)

Breathing defines the primary function of the respiratory system—the act of moving air in and out of the lungs. Inhalation brings oxygen-rich air into the lungs, and exhalation pushes air out, creating the ventilation that makes gas exchange possible. Without this airflow, oxygen can’t reach the blood and carbon dioxide can’t be expelled, so the body’s cells can’t receive oxygen or rid themselves of waste gas.

Gas exchange—where oxygen moves from the alveoli into the blood and carbon dioxide moves into the alveoli to be exhaled—happens after air reaches the lungs. It’s a crucial step, but it requires the ventilation process to occur first. Filtering of air is a supportive, protective function of the nasal passages and upper airways, not the primary job of the respiratory system.