The HEART

6. - A type of white blood cell that engulfs and digests bacteria and other harmful substances.
8. - Red blood cells that transport oxygen throughout the body.
10. - The process of breathing; how oxygen is taken into the body and carbon dioxide is released.
13. - Relating to the system that moves blood through the body.
14. - Platelets that play a role in blood clotting to prevent bleeding.
16. - A valve with two flaps, located between the left atrium and left ventricle.
18. - Blood vessels that carry blood away from the heart to other parts of the body.
20. - White blood cells that help protect the body from infections.

1. - A part of the heart (SA node) that regulates heartbeat by sending electrical signals.
2. - Crescent-shaped; refers to valves in the heart that control blood flow out of the ventricles.
3. - Related to the lungs or the pulmonary artery, which carries blood to the lungs.
4. - A thin membrane that lines the inside of the heart.
5. - The two lower chambers of the heart that pump blood out of the heart.
7. - A protein in red blood cells that binds with oxygen and gives blood its red color.
9. - A chemical element in the blood, found in carbon dioxide, a waste product of respiration.
11. - The two upper chambers of the heart that receive blood.
12. - A valve with three flaps, located between the right atrium and right ventricle.
15. - Small blood vessels where the exchange of oxygen, nutrients, and waste occurs between blood and cells.
17. - The phase of the heartbeat when the heart muscles contract and pump blood.
19. - The wall that divides the left and right sides of the heart.