What term describes the exchange of oxygen and carbon dioxide at the lung and tissue capillaries?

What term describes the exchange of oxygen and carbon dioxide at the lung and tissue capillaries?

• A. Respiration
• B. Circulation
• C. Metabolism
• D. Perfusion

Answer: (A)

Gas exchange of oxygen and carbon dioxide at the lung and tissue capillaries is respiration. This term covers both external respiration in the lungs, where O2 moves from alveolar air into the blood and CO2 moves from blood into alveolar air to be exhaled, and internal respiration in the tissues, where O2 moves from blood into cells and CO2 moves from cells into the blood. The driving force is diffusion down partial pressure gradients: O2 diffuses into blood, CO2 diffuses out into the air we exhale. In the blood, oxygen largely binds to hemoglobin, while carbon dioxide is carried mainly as bicarbonate. The other terms describe different processes: circulation is the transport of gases by the bloodstream, metabolism is the cellular use of oxygen to produce energy, and perfusion is the blood flow to tissues.

Gas exchange of oxygen and carbon dioxide at the lung and tissue capillaries is respiration. This term covers both external respiration in the lungs, where O2 moves from alveolar air into the blood and CO2 moves from blood into alveolar air to be exhaled, and internal respiration in the tissues, where O2 moves from blood into cells and CO2 moves from cells into the blood. The driving force is diffusion down partial pressure gradients: O2 diffuses into blood, CO2 diffuses out into the air we exhale. In the blood, oxygen largely binds to hemoglobin, while carbon dioxide is carried mainly as bicarbonate. The other terms describe different processes: circulation is the transport of gases by the bloodstream, metabolism is the cellular use of oxygen to produce energy, and perfusion is the blood flow to tissues.