Which term describes the process of gas exchange between air and blood in the lungs and tissues?

Which term describes the process of gas exchange between air and blood in the lungs and tissues?

• A. Excretion
• B. Afebrile
• C. Respiration
• D. Axillary

Answer: (C)

Gas exchange between air and blood in the lungs and tissues is called respiration. It occurs by diffusion across the membranes of alveoli and capillaries in the lungs and across capillary walls in tissues. Oxygen moves from areas of higher partial pressure in air or alveoli to lower pressure in blood, while carbon dioxide moves in the opposite direction to be expelled. In tissues, the pattern reverses: oxygen moves from blood to cells and carbon dioxide moves from cells to blood. Note that there’s a related term, cellular respiration, which is the metabolic use of oxygen by cells to generate energy—distinct from the gas exchange process described here. Other terms provided refer to different concepts (waste elimination, fever status, or anatomical location) and do not describe gas exchange.

Gas exchange between air and blood in the lungs and tissues is called respiration. It occurs by diffusion across the membranes of alveoli and capillaries in the lungs and across capillary walls in tissues. Oxygen moves from areas of higher partial pressure in air or alveoli to lower pressure in blood, while carbon dioxide moves in the opposite direction to be expelled. In tissues, the pattern reverses: oxygen moves from blood to cells and carbon dioxide moves from cells to blood. Note that there’s a related term, cellular respiration, which is the metabolic use of oxygen by cells to generate energy—distinct from the gas exchange process described here. Other terms provided refer to different concepts (waste elimination, fever status, or anatomical location) and do not describe gas exchange.