Your circulatory system controls the movement of blood through your heart and throughout your whole body. The blood circulates (moves) through our bodies in a continuous, closed loop. The movement is generated (started) by the pumping action of the heart. Your house also has a circulatory system, but instead of blood, it pushes water around. It is called the plumbing system and it is composed of pumps, pipes, and valves.

Both your body and your house have circulatory systems that operate using the same parts and concepts:

  • A pump: the heart (body); a mechanical pump (house).
  • Distribution vessels: arteries and veins (body); pipes (house).
  • Control valves: valves in the heart (body); faucets and the toilet lever (house).
  • Your circulatory system tranports both nutrition and waste: blood transports oxygen and nutrients and removes cell waste (body); the plumbing system carries both fresh and waste water (house).

One of the most important tasks of the circulatory system is to deliver nutrition and remove waste through blood — to and from the cells — at incredibly high speed. The size of your blood vessels controls the speed of blood flow: in large vessels the flow is slow, while in small vessels it speeds up. This is because the same amount of blood needs to move through under the same pressure (put out by the pump of your heart). If the opening is smaller, the pressure will be greater and it will be pushed through faster.


1. Sketch ideas for your design, figuring out how the system will work to fill up all the cells at the same time.
2. Use the materials listed to construct your circulatory system.
3. Check to see whether or not you have any leaks in your pipes. Also check to see if you need to add any valves to control the flow of “blood.”
4. Pour water into the entry part of your circulatory system and watch how it flows!

Reflecting on what you’ve learned:

What could you change about your circulatory system in order for the ”blood” to flow to the cells more quickly? How about more slowly? How does the size of your pipes affect the speed of blood flow?

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