respiratory and circulatory system

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Across
  1. 2. The fluid that transports oxygen and nutrients throughout the body.
  2. 4. A gas that enters the blood in the lungs and is transported to body cells.
  3. 5. The smallest blood vessels, where substances are exchanged between the blood and body cells.
  4. 8. Blood vessels that carry blood back to the heart.
Down
  1. 1. The tiny air sacs in the lungs where oxygen enters the blood.
  2. 3. The muscular organ that pumps blood throughout the body.
  3. 6. Blood vessels that carry blood away from the heart.
  4. 7. The organs responsible for gas exchange in the respiratory system.