Inferior vena cava arterioles left ventricle oxygen inferior vena cava Aorta superior vena cava veins large arterioles left ventricle Blood superior vena cava left atrium arteries carbon dioxide Upper lower 1. From the the blood enters the 2. Systemic circulation begins in the 3. From here, the is pumped into the 4. It branches into which also divides into 5. The then branches out into 6. These tiny blood vessels are the sites for and exchange. 7. Capillaries combine to form and these veins return the blood back to the 8. The and the are the largest veins of the body. 9. The vein that returns the blood to the regions of the body is the 10. On the other hand, the vein that returns the blood to the regions of the body are the​