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Activity 5-1: The Direction of Blood Flow

PLAN

Summary Students recreate some of the experiments William Harvey performed. They use their hands and arms to investigate the one-way flow of blood from the body back to the heart. Students investigate the role of gravity and valves in the veins.

Objectives

Students:

\checkmark investigate the role of gravity as it affects blood flow in arms and hands.

\checkmark observe valves in the veins of the hand.

Student Materials

  • Activity Report
  • Clock or watch with a second hand

Teacher Materials

  • Activity Report Answer Key
  • Model from Activity 1-1: The Pathway of Blood through the Body
  • Siphon pump from Activity 2-2: The Siphon Pump

Advance Preparation

Gather the models and materials noted in Teacher Materials.

Estimated Time One 45-\mathrm{minute} period

Interdisciplinary Connections

Language Arts or Social Studies You may want to share with the language arts or social studies teacher that your students are learning about the contributions of William Harvey, the 17th-century scientist who studied the human circulatory system.

Prerequisites and Background Information

Students should be able to describe the circulation of blood. They should have some knowledge about the roles of arteries and of veins in circulation.

IMPLEMENT

Steps 1-3

Divide the class into lab partners. Refer students to Figure 5.3. Have one student do the experiment, while the other records the observations for Steps 1-5. Then have students exchange roles and repeat Steps 1-5.

Steps 4-5

Remind students how to take a pulse. You can refer them back to Figure 2.5 on page 24 in their books. Emphasize the importance of the one-way valve.

Steps 6-7

Make sure each member of the pair does the experiment described in Steps 1-5 while the other records the observations.

Extend Activity 5-1 by having students

  • research the work of William Harvey and other scientists who studied the circulatory system.
  • investigate valve abnormalities of the heart, which can cause heart murmurs and reduce circulation efficiency.

Helpful Hints

  • Students should work in pairs allowing sufficient time for all students to participate actively.
  • Students who have difficulty locating their own surface vessels can make observations on those of other students.
  • Allow ample time for discussion. This is a powerful opportunity for students to summarize, connect, and reinforce key concepts of the unit.
  • Relate this activity to the excessive distention of veins causing varicose veins and explain how to prevent and treat these problems.
  • Connect this activity to the experience of being light-headed as a result of standing up too quickly from a resting position, which causes insufficient flow of blood to the head region.

ASSESS

Use the results of the activity and written responses to the Activity Report to assess if students can:

\checkmark explain how blood flows through the blood vessels.

\checkmark describe the one-way valve mechanism in the veins.

\checkmark explain how gravity affects blood flow in the arms and legs.

Activity 5-1: The Direction of Blood Flow - Activity Report Answer Key

  • Sample answers to these questions will be provided upon request. Please send an email to teachers-requests@ck12.org to request sample answers.
  1. Record your observations of the differences between your two arms and hands.
  2. Explain the observed differences between your two arms and hands.
  3. Attach a sheet of plain paper with a drawing of your hand showing the pattern of surface vessels.
  4. You observed the blood flowing in one direction in the veins as it returns to the heart. Name and describe as many features of the circulatory system as you can that help keep blood flowing in one direction throughout the circulatory system. (Hint: You may wish to refer to Activity 1-1: Pathway of Blood through Your Body.)
  5. Name additional factors responsible for the movement of blood through the circulatory system.
  6. How does the one-way system of blood flow help maintain homeostasis?

A suggested response will be provided upon request. Please send an email to teachers-requests@ck12.org.

The soldiers who guard Buckingham Palace in London, England do not move when they are on guard. They are known for their ability to stand still for very long periods of time. Some guards have fainted after only 30 minutes on duty. Why do you think this happened? What happened? How could the guard have prevented it?

Why is it more important for leg veins to have valves than neck veins?

Percentages of Blood Students make a circle graph that demonstrates the percentages of blood in different parts of the circulatory system.

At rest your heart pumps only 20 to 25\;\mathrm{percent} of the total blood volume in your body. What is the purpose of the other 75 to 80\;\mathrm{percent} of the blood? Where is this blood?

In which blood vessels does blood travel the most slowly? Why?

Pretend you are a drop of blood. What differences would you feel going to the heart through a vein than going from the heart through an artery?

Review Questions/Answers

  • Sample answers to these questions will be provided upon request. Please send an email to teachers-requests@ck12.org to request sample answers.
  1. In Section 3 you learned about arteries. In this section you learned about veins. Compare an artery and a vein. List four differences.
  2. Explain how blood gets back to your heart from your feet when you are walking. What factors help the return of venous blood to the heart? What makes it more difficult to return venous blood back to the heart?
  3. When you are resting, a greater percentage of your total blood volume is in your veins than when you are exercising. How is this possible?
  4. How is blood output from the heart related to blood return?
  5. Describe William Harvey's famous experiment. Include what he did and what conclusions he reached.

Activity 5-1 Report: The Direction of Blood Flow (Student Reproducible)

1. Record your observations of the differences between your two arms and hands.

2. Explain the observed differences between your two arms and hands.

3. Attach a sheet of plain paper with a drawing of your hand showing the pattern of surface vessels.

4. You observed the blood flowing in one direction in the veins as it returns to the heart. Name and describe as many features of the circulatory system as you can that help keep blood flowing in one direction throughout the circulatory system. (Hint: You may wish to refer to Activity 1-1: Pathway of Blood through Your Body.)

5. Name additional factors responsible for the movement of blood through the circulatory system.

6. How does the one-way system of blood flow help the body maintain homeostasis?

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