The _______ carries oxygen depleted blood away from the heart, while the ________ carries oxygen-rich blood back towards the heart.

The pulmonary artery carries blood from the right ventricle to the lungs, where it can pick up oxygen. Therefore, oxygen-depleted blood is carried in the pulmonary artery. This is contrary to most arteries, which typically carry oxygen-rich blood. Once the blood is oxygenated in the lungs, it returns to the heart at the left atrium through the pulmonary vein.
Once blood has been oxygenated and returns to the left side of the heart, it can be ejected by the left ventricle throughout the body via the aorta.
The vena cava returns oxygen depleted blood to the right atrium.