Be prepared. This can get messy and wet. Before starting, remind students to keep their area as dry as possible. Have an ample supply of sponges and toweling available.

*To produce a more effective container, use a sharp utility knife to carefully cut off and remove the upper neck of a large plastic container, as seen in the diagram. DO NOT have students perform this step.

ANSWERS

PART 1 -VESSEL FLOW
Procedure:

6. How does the effort compare to when the passageway was larger? (it is now more difficult to blow air through the constricted straw)
Does the appearance of the bubble stream change? How? (the bubbles get smaller)

Questions:

1. What did the clay represent? (material that accumulates on the inner sides of blood vessels or the constricted vessel walls)
2. What happens when the clay constricts the flow of air? (Gets more difficult to produce the steady stream of bubbles)
3. How did you compensate to maintain the steady bubble rate? (blew harder to increase the flow pressure)
4. Why was the depth of the straw marked and kept constant throughout the activity? (To maintain a control depth. At different depths, there is a difference in the amount of pressure needed to blow bubbles)

PART 2 - WALL WEAKNESS
QUESTIONS

1. What physical properties are essential in materials used to build both water pipes and organic vessels? (accept all reasonable answers including impermeable to fluid, physical strength, elastic strength, ability to seal leaks, etc.)
2. You have been asked to build a water pipe. Rate the following materials based upon their ability to withstand water pressure. wood, plastic, copper, modeling clay, (Accept all reasonable answers. However, you might wish to guide the discussion so that students compare and contrast the strength of a thin section of modeling clay with a thin section of plastic. )
3. Suppose you were patching a bicycle tire. How would the composition of the patch material affect the long-term success of your repair job? (the stronger the patch, the more successful the repair)

PROCEDURE

4. First, test the straw that is unobstructed (no inner plug). Take turns inserting your straws into the water-filled container. Make sure that the patch remains above the water level. Start blowing. What happens? (air bubbles are produced and the patch remains in place)

5. Now, take turns testing the obstructed straw. Insert the clay-plugged end into the water filled container. Keep the patch above the water level. Start blowing. What happens? (the patch separates from the straw allowing air to escape from this rip)

CRITICAL ANALYSIS OF YOUR MODEL
Consider the following questions and discuss them based on the above activity.

1. In your model, what does the plastic straw represent? (healthy blood vessel walls)
2. What does the flattened clay seal represent? (weak part of the vessel wall)
3. How can the experience above be applied to the obstruction/constriction of blood vessels? (it models the flow of a fluid through an open and constricted/blocked vessel)
4. Why does the seal rupture when air is blown through the plugged straw? (the plugged straw required a greater pressure to move fluid at an acceptable rate. At this higher pressure, the seal did not hold)

THINK ABOUT IT
Why did surgeons in the television program position the pressure release hole within the heart? Wouldn't it be safer and easier to locate (and later repair) this hole if it was positioned outside the heart? (This opening needs to be located so that any blood that seeps through it remains within the circulatory system. In order to transport gases, nutrients, and wastes, all blood must remain within the body's closed system of vessels. If blood leaks out of system, it is no longer transported to the lungs or circulated throughout the body.)

CURRICULUM LINK

Physical Science :

Patterns, Geometric Progression

Physics:

tissues, organs and systems  neural circuitry

Biology/Life Science:

Language arts

NATIONAL SCIENCE STANDARDS (Grades 5-8)

Science As Inquiry-Content Standard A

Students should develop abilities necessary to do scientific inquiry

Students should develop an understanding about scientific inquiry

Physical Science-Content Standard B

Students should develop an understanding of motion and forces

Life Science -Content Standard C

Students should develop an understanding of structure and function in living systems

Science and Technology-Content Standard E

Students should develop an understanding about science and technology

Students should develop abilities of technological design

History And Nature Of Science-Content Standard G

Students should develop and understanding of science as a human endeavor

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