Name: 
 

Human Circulatory System



Completion
Complete each sentence or statement.
 

1. 

The ___________    ___________ is the body system responsible for transporting materials to and from the cells of the body.
 

 

2. 

The system consists of three main parts: 1. __________  2. ___________ and
3. ________   ________
 

 

3. 

________ is the fluid that flows through the circulatory system and is composed of ______, ________, _______, and _____   ______.
 

 

4. 

Plasma is a mixture of _______, ________, _______, _______, _________ and other substances.
 

 

5. 

Plasma makes up the _______ part of  blood.
 

 

6. 

Most of the cells that make up blood are ____ blood cells.
 

 

7. 

Each red blood cell contains a protein called _____________, which clings to oxygen in the lungs and transports it throughout the body.
 

 

8. 

Red blood cells are made in _____   _________.
 

 

9. 

Before red blood cells enter the bloodstream they lose their ________ and other ________.
 

 

10. 

As a result of red blood cells losing their nuclei and organelles they cannot make proteins or repair themselves. What impact does this have on how long they can live?
 

 

11. 

White blood cells are responsible for ____________ the body against disease.
 

 

12. 

Some white blood cells take in and destroy _________ and _________.
 

 

13. 

Some white blood cells produce ____________, which are proteins that help destroy foreign substances.
 

 

14. 

Particles called __________ are also found in blood. They are formed when large cells in bone marrow pinch off bits of their cytoplasm.
 

 

15. 

Platelet play an important role in blood ____________.
 

 

16. 

Platelets ______ together to form plugs when a cut appears. They also release chemicals that react with proteins in plasma to form clots when necessary.
 

 

17. 

Blood is pumped through the circulatory system by the _______.
 

 

18. 

The heart is a muscular organ that pumps ___________ blood to the lungs.
 

 

19. 

The blood picks up _______ as it passes through the lungs. This _____________ blood is then returned to the heart, which pumps it to the rest of the body.
 

 

20. 

Blood travels in a network of hollow tubes called ______   _________.
 

 

21. 

There are ______ types of blood vessels.
 

 

22. 

__________ are blood vessels that carry blood away from the heart.
 

 

23. 

______ are blood vessels that carry blood back to the heart.
 

 

24. 

____________ are the smallest blood vessels and allow nutrients and gases to diffuse across their walls to and from cells.
 

 

25. 

Blood that leaves the lungs is ___________.
 

 

26. 

Refer to the following diagram.
human_circulatory_s_files/i0270000.jpg
 

 



 
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