2. a large molecule formed when oxygen combines with haemoglobin inside red blood cells

3. a special region of the haert which starts and controls the contractions of all the muscles of the heart

4. the yellow-coloured liquid of blood

5. circulation of blood through the lungs and the heart

6. circular biconcave red cells in blood that carry oxygen throughout the body

7. valves present at the beginning of the two large arteries leaving the heart to prevent the backflow of blood from the large arteries into the ventricles during ventricular relaxation

8. circulation of blood through the heart and all other parts of the body except the lungs

9. the liquid which bathes all body cells

10. the process of transporting organic nutrients from the leaves to other parts of a plant by phloem cells

11. a heart valve of three flaps which separates the right auricle from the right ventricle

12. people who can give their blood to any person with any type of blood

13. people who can receive any type of blood

14. blood vessels that return blood from tissues to the heart

15. the lower, larger chambers of the heart which pump blood into the auricles

16. blood vessels formed by capillaries joining together. Eventually they joined together to form veins

17. round or irregular colourless cells in the blood for body defence

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