Section

1

The Body’sTransport System

Objectives

After this lesson, students will be able to

D.3.1.1

Explain the functions of the cardiovascular system.

D.3.1.2

Describe the structure and function of the heart.

D.3.1.3

Sequence the path taken by blood through the cardiovascular system.

Target Reading Skill

Sequencing

Explain that organizing information from beginning to end helps students understand a step-by-step process.

Answers

Bottom oval: Left side of heart; left oval: Body

Teaching Resources

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Transparency D21

Preteach

Build Background Knowledge

Transportation Systems

Display a map of a subway, bus, train, or local highway system. Ask:

What is the function of this transportation system?

(To pick up and deliver passengers at various points along a route)

Tell students that the cardiovascular system transports blood and other materials through the body in the same way. They will learn how in this chapter.

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Skills Focus

Inferring

Materials

newspapers, paper towels, two large plastic containers, cup with capacity of about 60 mL, watch or clock with a second hand

Time

20 minutes

Tips

Set up with newspapers, towels, or other materials for quick cleanup. Put large plastic containers in a

larger container to catch spills. Advise students to wear aprons. Consider doing this activity outdoors.

Expected Outcome

Results will vary. Students probably cannot make 75 transfers of water.

Think It Over

The heart is very strong to be able to pump continuously and at the speed it does.

1 The Body’s Transport System

How Hard Does Your Heart Work?1. Every minute, your heart beats about 75 to 85 times. With

each beat, it pumps about 60 milliliters of blood. Can you work as hard and fast as your heart does?

2. Cover a table or desk with newspapers. Place two large plastic containers side by side on the newspapers. Fill one with 2.5 liters of water, which is about the volume of blood that your heart pumps in 30 seconds. Leave the other container empty.

3. With a plastic cup that holds about 60 milliliters, transfer water as quickly as possible into the empty container,

trying not to spill any. CAUTION: Wipe up spills on the floor immediately. Have a partner time you for 30 seconds. As you work, count how many transfers you make in 30 seconds.

4. Multiply your results by 2 to find the number of transfers in 1 minute.

Think It OverInferring Compare your performance with the number of times your heart beats every minute. What do your results tell you about the strength and speed of a heartbeat?

Reading PreviewKey Concepts• What are the functions of the

cardiovascular system?

• What is the structure and function of the heart?

• What path does blood take through the cardiovascular system?

Key Terms• cardiovascular system • heart • atrium • ventricle • valve • pacemaker • artery • capillary • vein • aorta

Target Reading SkillSequencing As you read, make a cycle diagram like the one below that shows the path that blood follows as it circulates throughout the body. Write each step of the pathway in a separate circle.

Late at night, a truck rolls through the darkness. Loaded withfresh fruits and vegetables, the truck is headed for a city super-market. The driver steers off the interstate and onto a smallerhighway. Finally, after driving through narrow city streets, thetruck reaches its destination. As dawn breaks, store workersunload the cargo. At the same time, a garbage truck removesyesterday’s trash and drives off down the road.

The Cardiovascular SystemLike the roads that link all parts of the country, your body hasa “highway” network, called the cardiovascular system, thatlinks all parts of your body. The cardiovascular system, alsocalled the circulatory system, consists of the heart, blood ves-sels, and blood. The cardiovascular system carries neededsubstances to cells and carries waste products away fromcells. In addition, blood contains cells that fight disease.

Right sideof heart

Lungs

Pathway of Blood

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Instruct

The Cardiovascular System

Help Students Read

Previewing Visuals

Before students read, have them look at the images in this section and predict what they are about to read. The arrows in the visuals might suggest that they will be learning about pathways and the direction of blood flow in the body.

Teach Key Concepts

System Functions

Focus

Remind students that the cardiovascular system removes as well as delivers materials.

Teach

Ask:

What materials does the cardiovascular system deliver throughout the body?

(Oxygen and glucose)

How does the cardiovascular system get rid of carbon dioxide?

(Carbon dioxide is passed from cells into the blood, and then carried to the lungs, where it is exhaled.)

Refer students to Figure 1. Ask:

Why do you think the lungs have a dense network of blood vessels?

(The lungs are the only place where the exchange of gases between the body and the environment occurs, so many blood vessels must be in the lungs to do this work quickly and efficiently.)

Apply

Display two 2-liter bottles and one 1-liter bottle, or an equivalent capacity in other containers. Tell students that an adult of average size has 5 liters of blood circulating at any one time—an amount that would fill the containers.

learning modality: visual

Teaching Resources

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Independent PracticeTeaching Resources

•

Guided Reading and Study Worksheet:

The Cardiovascular System

Student Edition on Audio CD

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Monitor Progress L2

Answers

Figure 1

Needed materials: oxygen and glucose; waste product: carbon dioxide

It transports cells that attack disease-causing microorganisms.

Heart

Blood vesselsin lungs

Key

Oxygen-rich blood

Oxygen-poor blood*

*Note: Blood is not actually blue in color.

FIGURE 1The Cardiovascular System The blood vessels of the cardiovascular system reach throughout the entire body. Blood flows through these vessels to every organ in the body. Classifying Name one needed material and one waste product transported by the cardiovascular system.

Delivering Needed Materials Most substances that needto get from one part of the body to another are carried byblood. For example, blood carries oxygen from your lungs toyour other body cells. Blood also transports the glucose yourcells use to produce energy.

Removing Waste Products The cardiovascular system picksup wastes from cells. For example, when cells break down glucose,they produce carbon dioxide as a waste product. The carbon diox-ide passes from the cells into the blood. The cardiovascular systemthen carries carbon dioxide to the lungs, where it is exhaled.

Fighting Disease The cardiovascular system also transportscells that attack disease-causing microorganisms. This processcan help keep you from becoming sick. If you do get sick, thesedisease-fighting blood cells will kill the microorganisms and helpyou get well.

How does the cardiovascular system help fight disease?

Differentiated Instruction

English Learners/Beginning

Vocabulary: Link to Visual

Refer students to Figure 2, and point out the parts of the heart as you read the captions. Make sure students understand that

right

and

left

are correct, and that the diagram is positioned as if looking at another person. Distribute an unlabeled diagram and have students label and color in the right and left atria and ventricles.

learning modality: visual

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English Learners/Intermediate

Vocabulary: Link to Visual

Have students do the beginning-level activity. Then pair students with English-proficient students to write four sentences describing the functions of the right and left atria and ventricles in their own words.

learning modality: verbal

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The Heart

For:

The Heart Activity

Visit:

PHSchool.com

Web Code:

cep-4031

Students learn the parts of the heart and see the flow of blood through the heart.

Teach Key Concepts

The Heart

Focus

Refer students to Figures 2 and 3.

Teach

Ask volunteers to read the descriptions of the parts of the heart in Figure 2. Explain that the human heart has four chambers. Ask:

What are the four chambers of the heart?

(Right atrium, right ventricle, left atrium, left ventricle)

Ask:

Which chambers contain oxygen-rich blood?

(The left atrium and left ventricle)

Explain that the valves separate the chambers from each other and from other parts of the body. Valves are located between the left atrium and the left ventricle, the right atrium and the right ventricle, and the right ventricle and the artery to the lungs. Have students look at Figure 3. Then ask:

Where in Figure 2 is this valve shown?

(Between the right ventricle and the artery to the lungs)

Show the transparency of Figure 2 and have individual students state each step in the flow of blood through the heart while you trace it with a pencil eraser or other object.

Apply

Point out that the walls of the ventricles are much thicker than the walls of the atria. Ask:

How could having thick walls benefit the ventricles?

(Thick walls give ventricles the muscular strength to pump blood out of the heart.)

Extend

The Active Art will show students how the heart pumps.

learning modality: visual

Teaching Resources

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Right AtriumThe right atrium receives blood from the body that is low in oxygen and high in carbon dioxide.

Right VentricleThe right ventricle pumps oxygen-poor blood to the lungs.

SeptumThe septum prevents oxygen-rich and oxygen-poor blood from mixing in the heart.

AortaThe aorta carries blood from the left ventricle to the body.

Left AtriumOxygen-rich blood moves from the lungs into the left atrium.

Left VentricleThe left ventricle pumps oxygen-rich blood to all parts of the body.

Artery from heart to lungs

Major vein from lower body to heart

Major vein from upper body to heart

The HeartWithout the heart, blood wouldn’t go anywhere. The heart is ahollow, muscular organ that pumps blood throughout thebody. Your heart, which is about the size of your fist, is locatedin the center of your chest. The heart lies behind the sternum(breastbone) and inside the rib cage. These bones protect theheart from injury.

Each time the heart beats, it pushes blood through theblood vessels of the cardiovascular system. The heart is madeof cardiac muscle, which can contract over and over withoutgetting tired. Figure 2 shows the structure of the heart.

For: The Heart activity Visit: PHSchool.comWeb Code: cep-4031

FIGURE 2

The HeartEvery second of your life, your heart pumps blood through your body. In a year, the heart pumps enough blood to fill more than 30 competition-size swimming pools.

Differentiated Instruction

Use Visuals: Figure 3

How Heart Valves Work

Focus

Remind students that valves are like one-way doors in the heart.

Teach

Ask:

Which way does the blood move through this valve?

(Up from the left through the open valve)

Apply

Ask students to predict what would happen if the blood began to flow backward.

(The valve would close and would prevent backward flow.)

learning modality: visual

Observing Your Heartbeat

Materials

stethoscope

Time

15 minutes

Focus

Explain that you can hear the sound of your valves closing by using a stethoscope.

Teach

Have students use the stethoscope to listen to their own heartbeats. (After each use, use rubbing alcohol to clean the parts of the stethoscope that are inserted into the ears.) Then have students describe the sound of the beating heart. Ask:

What sounds do you hear as your heart beats?

(There is a deeper sound, the “lub,” and a higher sound, the “dup.”)

Apply

Ask:

How do the sounds of the heartbeat relate to the muscle contractions in the heart?

(The “lub” sound comes from the closing of the valves between the atria and ventricles, while the “dup” sound comes from the closing of the valves between the ventricles and the blood vessels.)

learning modality: kinesthetic

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Special Needs

Model Heart

Have students examine a model heart with removable parts. Invite students to hold each part of the heart as you describe its function. Point out the difference in the size of the chambers and the thickness of the walls. Have students describe the different sizes of the blood

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vessels that lead in and out of the chambers. Give each student a beanbag or small, soft ball. Demonstrate how to squeeze the item at a steady rate to approximate 80 beats per minute, then have them do it. Emphasize that the heart works continuously like this for a person’s lifetime.

learning modality: kinesthetic

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Drawing

Have students draw a heart, label its chambers, and write brief captions describing the function of each chamber. Have students place their drawings in their portfolios.

Answer

Figure 3

Valves prevent blood from flowing backward.

FIGURE 3Open and Closed Heart Valves As blood flows out of the heart and toward the lungs, it passes through a valve like the one in the photograph. Applying Concepts What is the function of a closed heart valve?

Open Valve Closed Valve

The Heart’s Structure Notice in Figure 2 that the heart hasa right side and a left side. The right side of the heart is com-pletely separated from the left side by a wall of tissue calledthe septum. Each side has two compartments, or chambers—an upper chamber and a lower chamber. Each of the twoupper chambers, called an atrium (AY tree um) (plural atria),receives blood that comes into the heart.

Each lower chamber, called a ventricle, pumps blood out ofthe heart. The atria are separated from the ventricles by valves.A valve is a flap of tissue that prevents blood from flowingbackward. Valves are also located between the ventricles and thelarge blood vessels that carry blood away from the heart.

How the Heart Works The action of the heart has two mainphases. In one phase, the heart muscle relaxes and the heart fillswith blood. In the other phase, the heart muscle contracts andpumps blood forward. A heartbeat, which sounds somethinglike lub-dup, can be heard during the pumping phase.

When the heart muscle relaxes, blood flows into the cham-bers. Then, the atria contract. This muscle contraction squeezesblood out of the atria, through the valves, and into the ventricles.Next, the ventricles contract. This contraction closes the valvesbetween the atria and ventricles, making the lub sound andsqueezing blood into large blood vessels. As the valves betweenthe ventricles and the blood vessels snap shut, they make the dupsound. All of this happens in less than a second.

The Force of the Ventricles When muscle cells in the ven-tricles contract, they exert a force on the blood. A force is a pushor a pull. The force exerted by the ventricles pushes blood out ofyour heart and into arteries.

The contraction of the left ventricle exerts much more forcethan the contraction of the right ventricle. The right ventriclepumps blood only to the lungs. In contrast, the left ventriclepumps blood throughout the body.

Interpreting Pulse Data

Materials watch with a second hand

Time 10 minutes each day over one week

Focus Remind students that heart rate changes with changing oxygen needs.

Teach Show students how to locate their pulse by placing the index finger of one hand on the other wrist at the base of the thumb and moving the fingers slightly until the pulse is felt. Explain that the pulse is caused by a spurt of blood passing through an artery. By measuring their pulse, students can measure their heart rate. Have them count the number of beats in the pulse for exactly one minute, and allow time for practice. Then direct students to take their pulse three times a day for one school week—when they wake up in the morning, after exercising, before going to bed—and record their pulse rates in data tables. CAUTION: Advise students not to exercise if they have a medical condition that rules out vigorous exercise. At the end of the week, ask students to look for patterns in their data.

Apply Ask: How does your heart rate at certain times of the day or during certain activities relate to your body’s need for oxygen at that time? (The heart rate increases when there is a high demand for oxygen.) learning modality: logical/mathematical

Two Loops

Teach Key ConceptsFollowing the Two-Looped PathFocus Refer students to Figure 5.

Teach Have students place a finger on the right atrium and follow the arrows to trace the path of blood as you read the passage. Then ask: What is the difference between arteries and veins? (Arteries carry blood away from the heart; veins carry blood to the heart.) What are the two loops of blood flow? (Heart to the lungs and back to the heart; heart to the body and back to the heart)

Apply Ask: When blood is pumped to the body cells, is it oxygen-rich? (Yes; it has just come from the lungs where it released carbon dioxide and picked up oxygen.) learning modality: visual

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Skills Focus Creating data tables

Materials paper and pencil

Time 15 minutes

Tips Suggest that students’ tables contain a column for volume of blood per minute at rest and volume of blood per minute during vigorous exercise.

Expected Outcome The skeletal muscles need extra oxygen and glucose during exercise, so the amount of blood flowing to other organs is adjusted.

Extend Have students graph the data. learning modality: logical/mathematical

Regulation of Heartbeat A group of heart cells called thepacemaker sends out signals that make the heart muscle con-tract. The pacemaker is located in the right atrium of the heart.

The pacemaker constantly receives messages about thebody’s oxygen needs. It then adjusts the heart rate to match.For example, your heart beats much faster when you are exer-cising than when you are sitting quietly. When you exercise, theentire process from the beginning of one heartbeat to thebeginning of the next can take less than half a second. Yourmuscles need more oxygen during exercise. Your rapid heart-beat supplies blood that carries the oxygen throughout yourbody.

In some people, the pacemaker becomes damaged as aresult of disease or an accident. Damage to the pacemakeroften results in an irregular or slow heartbeat. In the 1950s,doctors and engineers developed an artificial, battery-operatedpacemaker. Modern artificial pacemakers are implantedbeneath the skin and are connected by wires to the heart. Tinyelectrical impulses travel from the battery through the wires,and make the heart contract.

What is the function of the heart’s pacemaker?

Two LoopsAfter leaving the heart, blood travels in blood vessels throughthe body. Your body has three kinds of blood vessels—arteries,capillaries, and veins. Arteries are blood vessels that carryblood away from the heart. From the arteries, blood flows intotiny, narrow vessels called capillaries. In the capillaries, sub-stances are exchanged between the blood and body cells. Fromcapillaries, blood flows into veins, blood vessels that carryblood back to the heart.

Pattern of Blood Flow The overall pattern of blood flowthrough the body is something like a figure eight. The heart isat the center where the two loops cross. In the first loop,blood travels from the heart to the lungs and then back to theheart. In the second loop, blood is pumped from the heartthroughout the body and then returns again to the heart.The heart is really two pumps, one on the right and one onthe left. The right side pumps blood to the lungs, and the leftside pumps blood to the rest of the body.

FIGURE 4An Artificial Pacemaker This pacemaker has been implanted beneath a patient’s skin and connected with wires to the heart. The pacemaker will regulate the patient’s heartbeat.

Creating Data TablesScientists measured the vol-ume of blood that different organs receive, at rest and during vigorous exercise.

• At rest, the organs of the abdomen received about 1,400 mL of blood per minute (mL/min). During vigorous exercise, they received 600 mL/min.

• At rest, skeletal muscles received 1,200 mL/min. During vigorous exercise, they received about 12,500 mL/min.

• At rest, the kidneys received 1,100 mL/min. During vigorous exercise, they received about 600 mL/min.

Create a table to record these data. Then, use the data to explain why some organs receive more blood during exercise than others.

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Differentiated Instruction

Teaching Resources

• Transparency D24

Address Misconceptions

The Color of BloodFocus Some students may think that some blood is actually blue.

Teach Tell students that oxygen-poor blood is dark red, not blue. Illustrations of the cardiovascular system often show vessels in blue and red to distinguish vessels that carry oxygen-rich blood from those that carry oxygen-poor blood. Ask: Why is some blood dark red? (It contains little oxygen.) Where does it change to bright red? (In the lungs; wastes move from blood to the air, while oxygen in air moves into blood. Blood that is rich in oxygen is bright red.)

Apply Ask: Why is blood in the veins traveling from the body to the right atrium dark red? (Body cells use up the oxygen in the blood and add wastes, so the blood in these veins would be low in oxygen and high in wastes—dark red.) learning modality: verbal

CirculationShow the Video Field Trip to let students experience the intense exercise regimens of top athletes and understand how the training helps to improve the efficiency of the cardiovascular system. Discussion question: How does the circulatory system get rid of carbon dioxide waste in the blood? (The blood caries the carbon dioxide from the cells to the lungs, where it is exhaled into the air.)

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Gifted and TalentedResearching Pacemakers Have students research artificial pacemakers that are sensitive to changes in body temperature and oxygen needs. Ask: Why would these be more efficient than pacemakers that do

not have these functions? (They could match the person’s heart rate with his or her activity level.) Have students present their findings in a poster or visual presentation to the class. learning modality: visual

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Skills Check Have students make flowcharts of the path of blood from one point until it reaches the same point again.

AnswersFigure 5 The lungs

It adjusts the heart rate to meet the body’s oxygen needs.

Arteries to lungs

Rightatrium

Leftatrium

Veins fromlungs

Rightventricle

Leftventricle

Loop One

Loop Two

Arteries to body

Veins from body

Loop One:to the lungs and back to the heart

Loop Two:to the bodyand back to the heart

Blood travels in only one direction. If you were a drop ofblood, you could start at any point and eventually return to thesame point. The entire trip would take less than a minute. Asyou read about the path that blood takes through the cardio-vascular system, trace the path in Figure 5.

Loop One: To the Lungs and Back When blood from thebody flows into the right atrium, it contains little oxygen but alot of carbon dioxide. This oxygen-poor blood is dark red. Theblood then flows from the right atrium into the right ventricle.Then, the ventricle pumps the oxygen-poor blood into thearteries that lead to the lungs.

As blood flows through the lungs, large blood vessels branchinto smaller ones. Eventually, blood flows through tiny capillar-ies that are in close contact with the air that comes into thelungs. The air in the lungs has more oxygen than the blood inthe capillaries. Therefore, oxygen moves from the lungs into theblood. For the same reason, carbon dioxide moves in the oppo-site direction—from the blood into the lungs. As the bloodleaves the lungs, it is now rich in oxygen and contains little car-bon dioxide. This blood, which is bright red, flows to the leftside of the heart and will be pumped through the second loop.

FIGURE 5Direction of Blood Flow Blood circulates through the body in two loops, with the heart at the center. Loop one goes from the heart to the lungs and back. Loop two circulates blood throughout the rest of the body. Interpreting Diagrams Where does the blood that enters the left atrium come from?

Video PreviewVideo Field TripVideo Assessment

Circulation

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AnswerThe aorta

Assess

Reviewing Key Concepts1. a. Carrying needed substances to cells, carrying waste products away from cells, and transporting cells that fight disease b. Oxygen and glucose are transported to cells, while carbon dioxide and other wastes are transported away from cells.2. a. Right atrium, right ventricle, left atrium, and left ventricle; the septum and valves b. Pumps blood through the blood vessels of the cardiovascular systemc. Blood would flow backwards, from the right ventricle to the right atrium.3. a. The right atrium b. The right ventricle c. The blood leaving the right ventricle is oxygen-poor, while the blood leaving the left ventricle is rich in oxygen; the lungs

ReteachHave pairs of students make a set of note cards that describes each chamber in the heart, major blood vessels, and places in the body where blood is transported. Have them shuffle the cards and take turns placing the cards in the correct order.

Performance AssessmentWriting Have students explain the role of the heart in the cardiovascular system.

Teaching Resources

• Section Summary: The Body’s Transport System

• Review and Reinforce: The Body’s Transport System

• Enrich: The Body’s Transport System

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Keep Students on Track See that students have sketched out the two loops correctly. Advise them to begin planning how they will construct their displays and to start a list of materials or equipment they will need. Ask them to think about how they will show movement of blood cells. Check to make sure that their plans are realistic.

Writing Mode Comparison

Scoring Rubric 4 Includes an appropriate comparison; describes similarities and differences on a point-by-point basis3 Includes an appropriate comparison, but lacks some detail2 Includes a weak comparison and has little detail.1 Includes a poor comparison

Section 1 Assessment

Target Reading Skill Sequencing Refer to your cycle diagram about the pathway of blood flow as you answer Question 3.

Reviewing Key Concepts1. a. Reviewing What three functions does the

cardiovascular system perform?b. Comparing and Contrasting Distinguish

between substances that the cardiovascular system transports to cells and substances that it transports away from cells.

2. a. Listing Name the four chambers of the heart. What structures in the heart separate one chamber from another?

b. Summarizing What function does the heart perform?

c. Predicting What would happen if the valve between the right atrium and right ventricle did not work properly?

3. a. Identifying Where does blood returning from the body enter the heart?

b. Sequencing Where does the blood move next?

c. Interpreting Diagrams Review Figure 5. How does the blood in the artery leaving the right ventricle differ from the blood in the artery leaving the left ventricle? To where does the artery leaving the right ventricle carry blood?

Comparison Paragraph Write a paragraph comparing the cardiovascular system in the body to a system of roads, telephone lines, or any other “network” you can think of. How are the two systems alike? How do they differ?

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Loop Two: To the Body and Back The sec-ond loop begins as the left atrium fills with oxy-gen-rich blood coming from the lungs. The bloodthen moves into the left ventricle. From the leftventricle, the blood is pumped into the aorta (ayAWR tuh), the largest artery in the body.

Eventually, after passing through branchingarteries, blood flows through tiny capillaries indifferent parts of your body, such as your brain,liver, and legs. These vessels are in close contactwith body cells. Oxygen moves out of the bloodand into the body cells. At the same time, carbondioxide passes from the body cells into theblood. This blood, which is low in oxygen, thenflows back to the right atrium of the heartthrough veins, completing the second loop.

What is the largest artery in the body?

FIGURE 6Getting Blood to Body Cells In loop two, oxygen-rich blood is pumped throughout the body. The oxygen moves out of the blood and into the body cells in this swimmer’s arms and legs.