| Word | Meaning |
| Blood vessel | A tube that blood flows through |
| Artery | A vessel that carries blood away from the heart |
| Vein | A vessel that brings blood back to the heart |
| Capillary | A very fine vessel that joins an artery to a vein |
| Arteriole | A small branch of an artery that divides into capillaries |
| Aorta | The largest artery in the body |
| Vena cava | One of the two largest veins of the body |
| Venule | A small vein |
| Atrium | An upper chamber of the heart that receives blood |
| Ventricle | A lower chamber of the heart that pushes blood out |
| Valve | A door-like flap that stops blood flowing backwards |
| Pericardium, myocardium, endocardium | The outer, middle and inner layers of the heart wall |
| Alveoli | Tiny air sacs in the lungs where gases are exchanged |