| A | B |
|---|
| Circulation | the transportation of blood throughout the body |
| Heart | muscular organ that pumps the blood |
| Atrium | an opening at the top of the heart |
| Ventricle | an opening at the bottom of the heart |
| Number of Chambers in the Human Heart | 4 |
| Pacemaker | the special group of cells that keeps the heart beating at a constant, steady pace |
| Heart Valve | a flap of tissue located between chambers to prevent blood from flowing backward |
| Pulmonary Circulation | the circulation of blood from the heart, to the lungs, and back to the heart |
| Systemic Circulation | the circulation of blood throughout the body, except through the heart and lungs |
| Coronary Circulation | the special type of circulation that occurs only in the heart |
| Blood Vessel | a special "closed" tube that transports blood |
| Arteries | special blood vessels that usually carry blood away from the heart; high in oxygen |
| Veins | special vessels that carry blood to the heart; high in carbon dioxide waste |
| Capillaries | special vessels that connect arteries and veins |
