External respiration is?

External respiration is?

• A. Glucose transport in blood
• B. Oxygen diffuses into tissues
• C. Oxygen diffuses into blood via capillaries
• D. Carbon dioxide diffuses into capillaries

Answer: (C)

External respiration is the gas exchange between air in the lungs and blood in the pulmonary capillaries. At the alveolar–capillary membrane, oxygen moves from the alveoli into the blood because alveolar oxygen tension is higher than blood oxygen tension, diffusing into the blood via the capillaries. Carbon dioxide moves in the opposite direction, from blood into the alveolar air to be exhaled. This process differs from internal respiration, which is gas exchange between blood and body tissues. The other options describe different processes: glucose transport in blood is not a respiratory process, and oxygen diffusing into tissues represents internal respiration rather than external respiration; carbon dioxide diffusing into capillaries would imply CO2 moving into blood, which is not what happens during external respiration.

External respiration is the gas exchange between air in the lungs and blood in the pulmonary capillaries. At the alveolar–capillary membrane, oxygen moves from the alveoli into the blood because alveolar oxygen tension is higher than blood oxygen tension, diffusing into the blood via the capillaries. Carbon dioxide moves in the opposite direction, from blood into the alveolar air to be exhaled. This process differs from internal respiration, which is gas exchange between blood and body tissues. The other options describe different processes: glucose transport in blood is not a respiratory process, and oxygen diffusing into tissues represents internal respiration rather than external respiration; carbon dioxide diffusing into capillaries would imply CO2 moving into blood, which is not what happens during external respiration.