i am doing a crossword puzzle for the circulatory and respiratory systems review. if you can say them all i will give you 22 points. if you need to know how many letters ask in comments.3.pumps blood to heart6.what returns fluid that leaks from capillaries back to the circulatory system7. branching system of tubes which sends air to the alveoli 9. contains blood with little oxygen and a lot of carbon dioxide15. a dangerous tumor in the respiratory system.16. muscle that relaxes when you exhale.19.moves substances through the body.down: 5.separates the atria from the ventricle ; keeps blood flowing one way8. thin walled blood vessel that allows for gas exchange11. hair like structures that line the trachea and nose12. receives blood from the lungs17. movement of air in and out of lungs18 location of gas exchange in the lungs20. oxygen transport blood component