Horizon Circulatory System

5. A hollow muscular organ that is the at the center of the circulatory system.
7. The name for the chambers that pump blood out of the heart.
8. The pair of organs where the exchange of carbon dioxide and oxygen take place.
10. The kind of blood that anyone can receive in a transfusion.
13. A protein that contains iron and binds chemically to oxygen.
14. The last name of the scientist who discovered blood types.
15. The part of the blood that form blood clots.
17. The largest vein in your body.
19. This makes up the middle layer of arteries and veins.
22. This is what the inner surface of blood vessels is made of.
23. The tiniest blood vessels that are only one layer thick.

1. The type of muscle that makes up the heart.
2. The part of the blood that fights disease.
3. The muscular wall that separates the two sides of the heart.
4. There are four of these in the heart and they keep blood from flowing backwards.
6. The blood vessels that carry deoxygenated blood to the heart.
9. The part of the blood that carries oxygen.
11. Blood is this type of tissue.
12. The largest artery in your body.
15. The liquid part of the blood.
16. The blood vessels that carry oxygenated blood away from the heart.
18. The name for the chambers that receive blood into the heart.
20. The name of the valve between the left atrium and the left ventricle.
21. Fluid that has leaked out of the circulatory system.