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Teaching Guide
Activity 3: Grades 5-8
One-Way Valves


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  1. What did the glove represent?
    (A one-way valve found within the heart or veins.)
  2. What did the plastic tubing represent?
    (A blood vessel or a section of the heart in which blood was confined.)
  3. Why did you invert the glove in step 9?
    (To simulate the backward flow of blood)
  4. Describe the mechanical action of the valve.
    (Water flowing in one direction kept the slits of the valve spread apart. When the direction of flow was reversed, the slits pressed in against each other. This clogged the valve and prevented any reasonable back flow.)


Veins Only
Although there are valves in veins to prevent the backward ebb of blood, no such parts are found in arteries. Why?
HINT: Consider the difference in pressure found within an artery and a vein.
(Because arteries extend from the heart, the high pressure within these vessels prevents any backward movement. Because veins return to the heart, the pressure is much lower and back flow can exist.)




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