1. Carbon dioxide diffuses from the blood to the alveoli and is released during exhalation. 2. Gas exchange takes place between the capillaries and alveoli in the lungs. 3. Inhaled oxygen enters the bloodstream through diffusion from the alveoli into the capillaries. 4. Oxygenated blood flows back to the heart through pulmonary vein. 5. The heart pumps deoxygenated blood that enters the lungs through the pulmonary artery. 6. The heart pumps the blood and enters the aorta, the oxygen, to be distributed throughout the body. A.1-4-3-6-2-5 C.6-2-1-3-4-5 B. 5 - 2 - 3 - 1 - 4 - 6 D. 6-4-1-3-2-5
