Which tiny vessels are the site where oxygen moves from red blood cells into body tissues?

Which tiny vessels are the site where oxygen moves from red blood cells into body tissues?

• A. Arteries
• B. Veins
• C. Capillaries
• D. Venules

Answer: (C)

Gas exchange happens most effectively across the thin walls of capillaries. These tiny vessels have walls only one cell thick, which lets oxygen move easily from the blood into the surrounding tissues. Hemoglobin releases oxygen as it encounters tissues with lower oxygen levels, and the oxygen then diffuses through the capillary wall into interstitial fluid and cells. At the same time, carbon dioxide produced by the cells diffuses from the tissues back into the blood to be carried away. Arteries deliver blood toward tissues, and veins carry it back to the heart, while capillaries are the network where this exchange occurs.

Gas exchange happens most effectively across the thin walls of capillaries. These tiny vessels have walls only one cell thick, which lets oxygen move easily from the blood into the surrounding tissues. Hemoglobin releases oxygen as it encounters tissues with lower oxygen levels, and the oxygen then diffuses through the capillary wall into interstitial fluid and cells. At the same time, carbon dioxide produced by the cells diffuses from the tissues back into the blood to be carried away. Arteries deliver blood toward tissues, and veins carry it back to the heart, while capillaries are the network where this exchange occurs.