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Activity 2-1: Exploring the Heart

PLAN

Summary Students dissect a mammalian heart. The sheep heart is an excellent specimen, since it is about the same size and shape as the human heart.

Objectives

Students:

\checkmark identify the anatomy of the heart.

\checkmark describe the functions of the heart chambers and valves.

\checkmark explain the pathway of blood through the heart.

Student Materials

  • Activity Reports 1, 2, and 3
  • Animal heart (sheep, cow, or pig); Tweezers; Scalpel; Scissors; Probes; Apron or smock; Plastic disposable gloves; Dissection pan; Paper towels; Plastic bag

Teacher Materials

  • Activity Reports Answer Keys
  • Newspaper to protect working surface
  • Container for used heart specimens
  • Soap and paper towels
  • Charts and other visuals showing the heart and circulation of blood

Advance Preparation

Purchase disposable gloves or obtain gloves donated by a local hospital, clinic, or doctor/dentist office.

Order mammalian hearts, such as cow, pig, or sheep. Contact a local butcher to make sure you can obtain hearts. Or you can order prepared dissection materials from the following.

Carolina Biological Supply Company, 2700 York Rd., Burlington, NC 27215. Call 1-800-334-5551.

Contact the American Heart Association for pamphlets, heart drawings, and other related materials.

Make arrangements with your custodian for disposal of used specimens. If possible, freeze the specimens before disposing of them.

Estimated Time Two or three 45-\mathrm{minute} periods

Interdisciplinary Connection

Art Students could build a life-size model of the heart using clay or another material.

Prerequisites and Background Information

Students should be familiar with the pathway of blood through the body and heart. An introduction to the anatomy of the heart will also be helpful.

Helpful Hints

  • Confirm that students can correctly identify the left and right sides of the heart specimen, the top and bottom, and the front and back.
  • Be sure to allow adequate time for cleanup.
  • The guideline in Step 6 of the Procedure will help in positioning the heart in its anatomically correct position.

IMPLEMENT

Introduce Activity 2-1 by demonstrating procedure Steps 1-6.

Steps 7-8

It can be difficult to find the structures within the heart. It often helps if the teacher finds the first structure and shows students. Then guide students as they find the other heart structures. When most students finish Steps 7-8 stop them and review as a group what they have discovered.

Steps 9-11

Follow the same process as described above for demonstration, modeling, guidance, and review. As students proceed, remind them to use Figures 2.2, 2.3, and 2.4 as models. But also assure them that the structures they are exploring in the real specimen can look different from those in a drawing. This is the reason it is helpful for the teacher to model and demonstrate some parts of the dissection.

Steps 12-14

Make sure students are pushing the straws through the openings and not through the walls separating the chambers of the heart.

Steps 15-18

As you review, remind students to answer the corresponding questions in their Activity Reports. Remind them that it's much easier and more accurate to answer the questions as they proceed through the exploration rather than to try to remember later.

The actual modeling and dissection will take approximately two 45-\mathrm{minute} periods. Stress the need for students to wash their hands thoroughly as the last step of cleanup each day. If the lab requires a second day make sure the specimens are stored in a refrigerator overnight.

Conclude Activity 2-1 by discussing what students observed and what they learned about the structure of a mammalian heart. Make sure students have completed their Activity Reports. And make sure the lab is cleaned and the specimens disposed of safely.

ASSESS

Use your observations of the students' dissection of an animal's heart, participation in the class discussions, and their written responses to Activity Reports 1 and 2 to assess if students can

\checkmark describe the general size of an animal's heart.

\checkmark identify the blood vessels (arteries and veins) that connect the heart with the rest of the body.

\checkmark identify the location and explain the function of the chambers and valves of the heart (vena cava, right atrium, left atrium, pulmonary artery, pulmonary vein, left ventricle, right ventricle, aorta, aortic valve, tricuspid valve, mitral valve, and pulmonary valve).

\checkmark demonstrate the direction of blood flow through the heart (vena cava, right atrium, right ventricle, pulmonary artery, lungs, pulmonary veins, left atrium, left ventricle, aorta).

\checkmark compare and contrast an animal heart and a human heart.

Activity 2-1: Exploring the Heart - Activity Reports 1, 2, and 3 Answer Keys

  • Sample answers to these questions will be provided upon request. Please send an email to teachers-requests@ck12.org to request sample answers.
  1. Explain why the muscle of the left ventricle is thicker than the muscle of the right ventricle.
  2. What is the function of the heart valves?
  3. What happens to the blood after passing from the right ventricle but before it enters the left atrium? What organ does the blood pass through? What gas does the blood receive? What gas does the blood give up?
  4. List in order those parts that determine the direction of blood flow through the heart. Start with the vena cava and include the following: vena cava, left atrium, right atrium, left ventricle, right ventricle, pulmonary artery, pulmonary vein, aorta.
  5. On the heart diagram below, label the following structures: vena cava, right atrium, left atrium, pulmonary artery, pulmonary vein, left ventricle, right ventricle, aorta, aortic valve, tricuspid valve, mitral valve, and pulmonary valve.
  6. How does the pulmonary artery differ from all other arteries? How does the pulmonary vein differ from all other veins? Why is this distinction important? What does it tell you about how the heart works?

The Right Side of the Heart

  1. Find a wavy-edged flap that has an opening on the top. This flap called the auricle (little ear) allows extra blood to collect in the chamber of the heart called the atrium. The vessels entering the right atrium are the superior and the inferior vena cava. These veins bring oxygen-poor blood back to the heart from the rest of the body. Describe the atrium, which is a receiving chamber for the heart.
  2. Use your finger to find the opening into the right atrium and push down. If your finger goes completely into the heart, then you have reached the right ventricle. Take your finger out and replace it with a straw. If you push the straw all the way down, it will be in both the right atrium and the right ventricle.
  3. Push on the straw until you can see it stretching the wall of the heart. Stick the point of the scissors through the heart wall to meet the tip of the straw. Cut all the way up to the top following the straw. Observe the inside of the heart. Find the inside of the atrium and the ventricle. Is there anything inside the heart?
  4. Look between the right atrium and the right ventricle. You can see the thin, transparent membranes that form the tricuspid valve. The tricuspid valve remains open during the filling of the right ventricle. When blood leaves the right ventricle through the pulmonary artery, the tricuspid valve closes (Iub sound). Describe the valve.
  5. Look at the open side of the heart. Poke the second finger of your right hand into the back of the lower chamber. After your finger comes out on top, put a straw in the opening. This marks the pulmonary artery. The pulmonary (semi-lunar) valve lies between the right ventricle and the pulmonary artery. Remember that all arteries carry blood away from the heart. This is the only artery in the body that carries blood low in oxygen. What is the reason for this?

The Left Side of the Heart

  1. Find the opening on the top of the left side of the heart. The opening leads to the left atrium. Put a straw where your finger was. Push it all the way down. After the blood leaves the lungs it returns to the heart through the pulmonary vein. (Remember that all veins carry blood to the heart.) Pulmonary veins are the only veins in the body that carry oxygenated instead of deoxygenated blood. The pulmonary veins bring oxygen-rich blood back into the left atrium.
  2. Poke your scissors through the point where you think the end of the straw would be. Cut until you see the end of the straw. The end of the straw is now in the left ventricle. The straw has passed through the mitral or bicuspid valve. How is the wall of the left ventricle (which you have just cut through) different from the wall of the right ventricle? Explain.
  3. Find the opening from the lower left ventricle towards the middle of the heart that leads to the outside. This is the aorta. Put a straw in the aorta. Which kind of blood, oxygenated or deoxygenated, flows through the aorta?
  4. Cut down the aorta toward the heart and observe the valve. This is the aortic semi-lunar valve. Describe the appearance of the valve.
  5. Can you find the two coronary arteries in the walls of the ventricles? Locate two tiny holes in the aorta just above the aortic valve. This is where the coronary arteries leave the aorta to transport nutrients and oxygen to the heart.

Is Pumping Hard Work? Students squeeze a tennis ball 70\;\mathrm{times} to see how often the heart pumps in one minute at rest. You can assign this activity in preparation for Activity 2-2: Siphon Pump.

Heartbeats Students time their pulses to determine heart rate and use these data to calculate number of heartbeats per day, per week, and per lifetime.

Word Origins Students research the word origins of anatomical terms related to the heart and lungs.

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

Your friend tells you that she has a “heart murmur.” What do you think this means?

Activity 2-2: Siphon Pump

PLAN

Summary

Students use a siphon pump to explore how the heart functions as a pump. They use a siphon to empty water from a bucket positioned higher into a bucket positioned lower. Then they use a siphon pump to move the water from the lower bucket to the higher bucket. A siphon uses gravity to move water, but the siphon pump can move water against gravity.

Objectives

Students:

\checkmark demonstrate how to use a siphon and a siphon pump to empty water from a container with and against gravity.

\checkmark compare the valves of the heart to the valves of the pump.

\checkmark compare the pumping action of the heart to the siphon pump.

\checkmark describe how the heart can pump blood throughout the body against gravity.

\checkmark explain how the heart functions as a double pump.

\checkmark describe how the heart as a muscle keeps pumping continuously.

Student Materials

  • Activity Report
  • Siphon pump with inlet and outlet hoses (available at Marine Stores—Tempco fuel pump); siphon pump, split lengthwise; 2 large containers (i.e., buckets, dishpans, etc.), filled 3/4 with water

Teacher Materials

  • Activity Report Answer Key
  • Split one siphon pump lengthwise so that the valves are visible; Towels or sponges to clean up water spills; Models students produced in Activity 1-1.

Advance Preparation

Cut convenient lengths of plastic tubing to be used for siphons.

Purchase siphon pumps from a local marine store. West Marine has locations across the country and will give you the location nearest you if you call 1-800-538-0775. If there is no store nearby, West Marine will ship you a catalogue from which the siphon pumps can be ordered.

Using a saw or sharp knife, split one pump lengthwise for a demonstration. (The industrial arts teacher may be able to help prepare your model cross section.)

Collect 2 buckets or dishpans for each lab station.

Estimated Time One 50-\mathrm{minute} period

Interdisciplinary Connections

Music Use the rhythm and beat of music to illustrate how the rhythm of the heartbeat is constant over time.

Math Students can calculate pump intake/output and relate that to total volume of water moved and to the intake/output of blood by the heart at rest.

Industrial Arts Students can design and make various one-way pumps.

Health Students can compare and evaluate the kinds of valves used in heart valve replacement.

Prerequisites and Background Information

The Siphon If there is a difference in pressure between the ends of a water-filled tube, water will flow through the tube from the area of greater pressure (head of pressure) to the area of lesser pressure.

The pressure differences depend on the length and diameter of the hoses. In other words, the length and the diameter of the hoses of the siphon tube and the siphon pump determine the rate at which water will flow.

The Siphon Pump The squeeze/fill cycle moves water through the pump from the inlet to the outlet hose. The heart has 2 pumps in it. This is like 2 siphon pumps together.

The heart cycle—fill-squeeze-fill-squeeze-fill-squeeze—is a cycle.

The squeezing of the water in the bulb creates a pressure head between the bulb and the outlet tube. Water moves from the bulb where pressure is high through the tube where pressure is lower.

The valves in the siphon pump keep the water from squirting backwards out of the pump back into the inlet tube.

When the pump is squeezed and released it fills up again with water because the relaxed pump chamber becomes an area of lower pressure compared to the water at the end of the inlet hose. So water flows into the pump from a region of greater pressure to a region of lower pressure until the pump is filled.

IMPLEMENT

Part A: How Does a Siphon Work?

You can do Activity 2-2 as a whole-class demonstration, in lab partner pairs, or divide the class into groups of 3-5.

Introduce Activity 2-2 by discussing the usefulness of siphons and siphon pumps. Some students may have fish aquariums or may be familiar with the use of siphons with mowers, boats, cars, etc.

Steps 1-4

Make sure students have placed their containers at different heights. This can be accomplished by using stools, chairs, lab tables, and the floor. Demonstrate how you can affect flow by moving the tubes or pinching them shut. Remind students that the bubbles need to be out of the submerged tubes for the siphon and the siphon pump to work efficiently.

Step 5

Challenge students to empty all of the water from the upper container into the lower container by using the siphon. Challenge them to not waste or lose any water. With care, they can move the water without any loss or mess.

Part B: How Does a Siphon Pump Work?

Steps 1-4

Demonstrate the difference between a siphon and a siphon pump. Then challenge students to move the water back up from the bottom container to the container on top. Again challenge them to do this without losing any water. Be aware that students may expect the water to move from the lower level to the higher level without pumping as it did when the water was siphoned from higher to lower. Discuss the difference between a siphon and a siphon pump.

Helpful Hints

  • Ask students to refer to their models from Activity 1-1 for comparison. Ask students—What part of the model can be compared to the siphon pump?
  • Emphasize the difference between the tube for the siphon and the siphon pump.
  • Point out that there is an arrow showing direction of flow on the outside of the pump bulb.
  • Holding 2 pumps together can demonstrate how the heart is actually a double pump.
  • Challenge students to keep the pumping rhythms constant by following the beat of a metronome.

Part C: How Is Your Heart like a Siphon Pump?

Steps 1-3

Demonstrate the similarity of a siphon pump to a fish heart. The fish heart is only one pump. Demonstrate how 2 siphon pumps together model the heart as a double pump. Make sure students are completing their Activity Reports as they progress.

Conclude Activity 2-2 by relating the cardiac cycle (systole and diastole) to the squeezing and filling of the pump. Discuss how the model is similar to and different from the human heart. Emphasize that the heart muscle must pump continuously to do the job of pumping blood to all parts of the body.

ASSESS

Use observations of students' use of the siphon pump and their written responses to the Activity Report to assess if students can:

\checkmark explain how a siphon uses gravity to move a liquid.

\checkmark explain how a siphon pump works against gravity to move a liquid.

\checkmark identify the components of a siphon pump (pump, valves, tubing, and so on).

\checkmark compare and contrast the siphon pump apparatus and the human heart.

\checkmark demonstrate how the heart is actually a double pump that pumps continuously.

\checkmark describe how the squeezing and filling of the pump can be an analogy to systole and diastole in the cardiac cycle.

\checkmark explain how the valves of the heart prevent blood from moving backwards.

Activity 2-2: Siphon Pump 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.

A: How Does a Siphon Work?

  1. Explain what happens when you plug both ends of the hose with your fingers, keep one end in the water, move the other end of the hose out of the bucket toward the empty bucket on the floor, and release your finger.
  2. What determines the amount of water per second that flows through the siphon?
  3. Based upon your observations, describe how a siphon works.

B: How Does a Siphon Pump Work?

  1. What causes water to move out of the siphon pump when you squeeze the bulb?
  2. What happens when you plug the outlet hose with your finger while you pump the bulb? Explain your answer.
  3. When you squeeze the bulb, why does the water go in only one direction out of the bulb?
  4. After you squeeze the pump, what causes it to fill up with water again?

C: How Is Your Heart Like a Siphon Pump?

  1. Imagine that the siphon pump represents the right side of your heart. What would the squeeze bulb represent? The outlet hose? The inlet hose?
  2. Imagine that the siphon pump represents the left side of your heart. What does the squeeze bulb represent? The outlet hose? The inlet hose? The valve?
  3. You have just named some similarities between your heart and the siphon pump. Now describe what is different about how the siphon pump and your heart work.

What's Your Cardiac Output Today? Students determine their cardiac output by taking their pulse and calculating the volume per pulse per minute per day.

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

When exercising your working muscles help return blood to the heart more quickly. Remember that the stroke volume is the amount of blood the heart pumps out with each squeeze. Does exercise increase or decrease the heart stroke volume? Explain.

Why do athletes often have lower resting heart rates than non-athletes? If their hearts don't beat as frequently why don't they faint from a shortage of blood in circulation?

Why can a fish get by with only one pump in its heart when you need two?

Imagine you are a drop of blood in the left atrium of the heart. Describe your voyage through the heart and body and back to the heart. Include labeled diagrams to illustrate your story.

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. What is the heart cycle?
  2. Describe the four steps in which blood flows through the heart. Draw a picture showing the path of blood from when it enters the right atrium until it leaves the left ventricle.
  3. What do heart valves do?
  4. How is a siphon pump most similar to a heart?
  5. When you hear your heart beat, what exactly are you hearing?
  6. What two properties of your heart can change to increase your cardiac output?

Activity 2-1 Report 1: Exploring the Heart (Student Reproducible)

1. Explain why the muscle of the left ventricle is thicker than the muscle of the right ventricle.

2. What is the function of the heart valves?

3. What happens to the blood after passing from the right ventricle but before it enters the left atrium? What organ does the blood pass through? What gas does the blood receive? What gas does the blood give up?

4. List in order those parts that determine the direction of blood flow through the heart. Start with the vena cava and include the following: vena cava, left atrium, right atrium, left ventricle, right ventricle, pulmonary artery, pulmonary vein, and aorta.

5. On the heart diagram below label the following structures: vena cava, right atrium, left atrium, pulmonary artery, pulmonary vein, left ventricle, right ventricle, aorta, aortic valve, tricuspid valve, mitral valve, and pulmonary valve.

6. How does the pulmonary artery differ from all other arteries? How does the pulmonary vein differ from all other veins? Why is this distinction important? What does it tell you about how the heart works?

Activity 2-1 Report 2: Exploring the Heart (Student Reproducible)

The Right Side of the Heart

7. Find a wavy-edged flap that has an opening on the top. This flap is in the chamber of the heart called the atrium. The vessels entering the right atrium are the superior and the inferior vena cava. These veins bring oxygen-poor blood back to the heart from the rest of the body. Describe the atrium, which is a receiving chamber for the heart.

8. Use your finger to find the opening into the right atrium and push down. If your finger goes completely into the heart, then you have reached the right ventricle. Take your finger out and replace it with a straw. If you push the straw all the way down, it will be in both the right atrium and the right ventricle.

9. Push on the straw until you can see it stretching the wall of the heart. Stick the point of the scissors through the heart wall to meet the tip of the straw. Cut all the way up to the top following the straw. Observe the inside of the heart. Find the inside of the atrium and the ventricle. Is there anything inside the heart?

10. Look between the right atrium and the right ventricle. You can see the thin, transparent membranes that form the tricuspid valve. The tricuspid valve remains open during the filling of the right ventricle. When blood leaves the right ventricle through the pulmonary artery, the tricuspid valve closes (Iub sound). Describe the valve.

11. Look at the open side of the heart. Poke the second finger of your right hand into the back of the lower chamber. After your finger comes out on top, put a straw in the opening. This marks the pulmonary artery. The pulmonary (semi-lunar) valve lies between the right ventricle and the pulmonary artery. Remember that all arteries carry blood away from the heart. This is the only artery in the body that carries blood low in oxygen. What is the reason for this?

Activity 2-1 Report 3: Exploring the Heart (Student Reproducible)

The Left Side of the Heart

12. Find the opening on the top of the left side of the heart. The opening leads to the left atrium. Put a straw where your finger was. Push it all the way down. After the blood leaves the lungs, it returns to the heart through the pulmonary vein. (Remember that all veins carry blood to the heart) Pulmonary veins are the only veins in the body that carry oxygenated instead of deoxygenated blood. The pulmonary veins bring oxygen-rich blood back into the left atrium.

13. Poke your scissors through the point where you think the end of the straw would be. Cut until you see the end of the straw. The end of the straw is now in the left ventricle. The straw has passed through the mitral or bicuspid valve. How is the wall of the left ventricle (which you have just cut through) different from the wall of the right ventricle? Explain.

14. Find the opening from the lower left ventricle towards the middle of the heart that leads to the outside. This is the aorta. Put a straw in the aorta. Which kind of blood, oxygenated or deoxygenated, flows through the aorta? Oxygenated blood flows through the aorta.

15. Cut down the aorta toward the heart and observe the valve. This is the aortic semi-lunar valve. Describe the appearance of the valve.

16. Can you find the two coronary arteries in the walls of the ventricles? Locate two tiny holes just above the aortic valve. This is where the coronary arteries leave the aorta to transport nutrients and oxygen to the heart.

17. Complete your examination and exploration of the heart specimen.

18. Follow directions from your teacher to complete your dissection and cleanup. Be sure you wash your hands thoroughly.

Activity 2-2 Report: Siphon Pump

A: How Does a Siphon Work?

1. Explain what happens when you plug both ends of the hose with your fingers, keep one end the water, move the other end of the hose out of the bucket toward the empty bucket on the floor, and release your finger.

2. What determines the amount of water per second that flows through the siphon?

3. Based upon your observations, describe how a siphon works.

B: How Does a Siphon Pump Work?

1. What causes water to move out of the siphon pump when you squeeze the bulb?

2. What happens when you plug the outlet hose with your finger while you pump the bulb? Exp your answer.

3. When you squeeze the bulb, why does the water go in only one direction out of the bulb?

4. After you squeeze the pump, what causes it to fill up with water again?

C: How Is Your Heart Like a Siphon Pump?

1. When you imagine that the siphon pump represents the right side of your heart, what does the squeeze bulb represent? The outlet hose? The inlet hose?

2. When you Imagine that the siphon pump represents the left side of your heart, what does the squeeze bulb represent? The outlet hose? The inlet hose? The valve?

3. You have just named some similarities between your heart and the siphon pump. Now describe what is different about how the siphon pump and your heart work.

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