2. superior vena cava
The superior vena cava carries deoxygenated blood to the heart. The blood comes from the upper body.

3. semi-lunar valves
These valves prevent the blood from flowing back into the ventricles of the heart when it pumps.

4. right atrium
This hollow chamber receives the deoxygenated blood from the body.
(Via the superior vena cava and the inferior vena cava.)

5. right atrioventricular valve
This valve prevents the blood flowing back into the atria when the heart pumps it into the ventricle.

6. right ventricle
This hollow chamber pumps the deoxygenated blood to the lungs.

7. inferior vena cava
The inferior vena cava carries deoxygenated blood to the heart. The blood comes from the lower body.

8. aorta
The aorta carries the oxygenated blood to the body.

9. pulmonary arteries
These vessels carry deoxygenated blood to the lungs.

10. pulmonary veins
These vessels carry oxygenated blood from the lungs into the heart.

11. left atrium
This hollow chamber receives the oxygenated blood from the lungs.
(Via the pulmonary veins.)

12. left atrioventricular valve
This valve prevents the blood flowing back into the atria when then heart pumps it into the ventricle.

13. left ventricle
This hollow chamber pumps the oxygenated blood to the body.