The RBC flows throw the pulmonary artery to the alveoli, where blood goes through capillaries.

The capillary walls contain tiny air sacks of oxygen. While the blood flows through, the air sacks release the oxygen into the blood, and carbon dioxide is taken out of the blood and into the alveoli, turning the blood red.

The oxygenated blood then travels back through veins to the left atrium

What happens to Wille next?