At the arterial end of the pulmonary capillaries,
A) O2 diffuses from the alveoli into the blood, while CO2 diffuses from the blood into the alveoli.
B) O2 diffuses from the blood into the alveoli, while CO2 diffuses from the alveoli into the blood.
C) both O2 and CO2 diffuse from the blood into the alveoli.
D) both O2 and CO2 diffuse from the alveoli into the blood.
E) O2 diffuses from the alveoli into the blood, but there is no net movement of CO2.

Question

Quizplus · Accepted Answer

At the arterial end of the pulmonary capillaries, oxygen (O2) diffuses from the alveoli, where its concentration is higher, into the blood, where its concentration is lower. Simultaneously, carbon dioxide (CO2) diffuses from the blood, where its concentration is higher, into the alveoli, where its concentration is lower, to be exhaled. This exchange facilitates the oxygenation of blood and the removal of carbon dioxide, a waste product of cellular metabolism.

At the Arterial End of the Pulmonary Capillaries