The components of the circulatory system

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Across
  1. 4. place where substances are exchanged between the blood and body cells
  2. 7. a flap of tissue that prevents blood from flowing backward
  3. 8. take up oxygen in the blood and deliver it to cells elsewhere in the body
  4. 9. the body's defense fighters
  5. 10. blood vessels that carry blood away from the heart
  6. 12. iron-containing protein that binds chemically to oxygen molecules
Down
  1. 1. largest artery in the body
  2. 2. (singular) lower chambers of the heart
  3. 3. the liquid part of blood
  4. 4. consists of the heart, blood vessels,and blood
  5. 5. a force exerted by blood against the walls of blood vessels
  6. 6. blood vessels that carry blood back to the heart
  7. 11. upper chambers of the heart
  8. 12. hollow, muscular organ that pumps blood throughout the body