| A | B |
|---|
| left atrium | Blood flows from the lungs into this upper part of the heart. |
| heart | It pumps blood to body cells. It's the power behind the circulatory system |
| left ventricle | This lower part of the heart accepts blood from the left upper part of the heart and then pumps the blood out to body cells. |
| septum | It separates the heart into right and left sides. |
| atrium | upper heart chamber |
| ventricle | lower heart chamber |
| valve | It opens to allow blood to go from the upper chamber to the lower chamber. Then it closes to prevent blood from backing up. |
| aorta | It carries blood away from the heart. It's the largest blood vessel. |
| artery | It carries blood away from heart. |
| vein | It carries blood back to the heart. |
| capillaries | They are very small blood vessels. |
| right atrium | Blood flows into this upper part of the heart first. |
| right ventricle | Blood flows from the right atrium into this lower part of the heart and then to the lungs. |
| circulatory system | It sends food and oxygen to body cells and carries CO2 and waste products away from cells. |
