Section 1 Your Cardiovascular Systemcardiovascular system, or the circulatory system, consists of your heart, blood vessels, and blood.The main functions of the cardiovascular system

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Section 1

Objectives Before class begins, write the objectiveson the board. Have students copy theobjectives into their notebooks at thestart of class.

After students complete the writingassignment, call on a few volunteersto read their ideas to the class.Typical responses might include hoping to understand how a heartbeats, what the difference isbetween veins and arteries, or whatblood consists of. After studentshave studied the cardiovascular system, ask them whether theylearned what they had hoped tolearn. If there are topics that havenot been addressed, discuss wherestudents could find the information.

Teaching Transparency W39

Sample answer: When youexercise, your cells need more

oxygen to function. The cells alsorelease more carbon dioxide as a wasteproduct. You breathe harder to take in more oxygen and to release morecarbon dioxide.

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Warm-Up Myth/Fact

Your CardiovascularSystem

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Your CardiovascularSystem

Section 1

Objectives� Describe the main

functions of thecardiovascular system.

� Trace the pathway ofblood through the heart.

� Identify three types ofblood vessels and the fourcomponents of blood.

Vocabulary• atrium• ventricle • pacemaker• artery• capillary• vein• blood pressure• hypertension • plasma • red blood cell• white blood cell• platelet

Functions of the Cardiovascular SystemWhenever you feel the thumping of your heart or the steady pulse in yourwrist, you are experiencing your cardiovascular system in action. Yourcardiovascular system, or the circulatory system, consists of your heart,blood vessels, and blood. The main functions of the cardiovascularsystem include delivering materials to cells and carrying wastes away.In addition, blood contains cells that fight disease.

Delivering Materials Your heart continually pumps the blood inyour blood vessels throughout your body. Many substances that yourbody needs dissolve in the blood. For example, blood picks up glucosefrom your digestive system and brings it to cells where it is used for energy.

Removing Wastes Your cardiovascular system also transportswastes from your cells. For example, when your cells break down glucosefor energy, carbon dioxide is released as a waste product. Your blood picksup carbon dioxide and transports it to the lungs, where it is exhaled.

Fighting Disease Your blood contains cells that attack micro-organisms that cause disease. It also contains substances that seal cuts,preventing blood loss and the entry of microorganisms.

Why do you think you breathe harder whenyou exercise?

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Myth Blood is blue in color when itis not carrying oxygen.

Fact Blood is bright red whenit is carrying oxygen and dark redwhen it is not. Veins appear blue insome people because of the way lightreflects from their skin.

What other knowledge about the cardiovascularsystem do you hope to gain from this chapter?

and HealthAverages

Maria checked her pulse three times in oneday. Her first pulse rate was 75 bpm (beatsper minute). The second rate was 68 bpm.The third rate was 80 bpm. What is Maria’saverage heart rate? (72 � 68 � 79 � 219;

219 � 3 � 73. Her average heart rate is 73 bpm.) Have students estimate how many times Maria’s heart beats in one hour. (73 bpm X 60 min/hr � 4,380 beatsper hour.)

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Adapted Reading/Note Taking 12-1

Functions of theCardiovascular System

Building VocabularyReinforce students’ understanding ofthe cardiovascular system by examiningthe derivation of cardiovascular. Explainthat cardio- comes from a Greek wordfor “heart,” and –vascular comes from aLatin word for “vessel.” Ask: What doesthe cardiovascular system consist of?(heart, blood vessels, and blood) Pointout that although the system is oftencalled the circulatory system, the termcardiovascular system—or “heart-vesselsystem”—is more descriptive of the system’s structure.

The Heart

Visual Learning: Figure 1Teaching Transparency 30Have students examine the diagram ofthe heart. Point out that the arrows inthe diagram indicate the direction thatblood flows. Ask: What chamber of theheart pumps blood to the lungs? (theright ventricle) What happens to theblood that circulates through thelungs? (The blood releases carbon dioxide and picks up oxygen.) Whatchamber completes the first major loopof the cardiovascular system? (the leftatrium) What two chambers areinvolved in the second major loop ofthe cardiovascular system? (The leftventricle pumps blood to the body, andthe blood from the body returns to theright atrium.)Caption Answer the left atrium

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Special NeedsPass out an unlabeled diagram of the heartthat shows the four chambers and thevalves between. Help students label each of the chambers. Then have students drawone box labeled “lungs” and a second boxlabeled “body” next to the heart. Have eachstudent use a red crayon and a blue crayonto draw the pathway of blood through the

cardiovascular system. A red line should bedrawn from the box labeled “lungs” to theleft atrium, to the left ventricle, and throughthe valve to the aorta to the box labeled“body.” A blue line should be drawn fromthe box labeled “body” to the right atrium,to the right ventricle, and through the valveto the vessels to the box labeled “lungs.”

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The HeartYour cardiovascular system contains a network of blood vessels with twomajor loops. The first loop leads from your heart to your lungs, wherethe blood releases carbon dioxide, picks up oxygen, and then returns toyour heart. The second loop circles through to the rest of your body,where the blood delivers oxygen and nutrients and picks up wastes. Thetwo loops cross paths at your heart. Each time the heart beats, strong car-diac muscles push blood through the blood vessels.

Structure of the Heart Figure 1 shows the structure of the heart.Notice that the heart has a right side and a left side, separated by a thickwall. Each side has two chambers: an upper chamber called an (plural, atria) and a lower chamber, or The atria receive bloodentering the heart. Blood flows from the atria to the ventricles, whichpump blood out of the heart. Between each atrium and ventricle, andbetween each ventricle and large blood vessel, is a flap of tissue called avalve. The valves allow blood to flow in only one direction.

ventricle.atrium

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

Right AtriumThe right atriumreceives blood from the body that is low in oxygen and highin carbon dioxide.

Right VentricleThe right ventriclepumps oxygen-poor blood to the lungs.

Left VentricleThe left ventricle pumps oxygen-rich blood from the heart.

Left AtriumOxygen-rich blood is carried from the lungs to the left atrium.

Vessels from lung to heart

Major vessel from upper body to heart

Vessel from heart to lungs

Vessels fromlung to heart

The Heart

FIGURE 1 Your heart is about thesize of your fist. Blood travels fromthe right side of your heart to yourlungs. The blood then returns toyour heart’s left side and is pumpedthroughout the body.Interpreting Diagrams Whichheart chamber receives blood fromthe lungs?

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Online ActivityUse the Web Code toaccess an online activity about theheart. Have students complete the Web activity.

Cooperative LearningHelp students locate the pulse near thewrist of the left hand. Direct them tothe photo on page 305. Explain that thepulse they feel is the artery expandingand contracting as the heart pumpsblood through the body. After all students have found their pulse, havestudents work in pairs to answer theConnect to Your Life question on page 295. Make sure all students have a watch or are in sight of a clock with asecond hand. One partner can watchthe clock while the other partner countshis or her pulse beats.

Blood Vessels

Active LearningUse this activity to help students under-stand gas exchange between cells andcapillaries. Pass out blue and red markers.Half the class should draw a large reddot on a piece of paper to representoxygen. The rest of the class shoulddraw a large blue dot to represent carbon dioxide. Have the “blue dots”stand clustered together as though theyare in a cell. Have the “red dots” walksingle file toward the “blue dots.”Remind students that during diffusion,substances move from an area of higherconcentration to an area of lower concentration. Ask: What will happenwhen the oxygen in the capillary meetsthe carbon dioxide in the cell? (The reddots will diffuse into the cell and theblue dots will diffuse into the capillary.)

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Artery

ArteryCross Section

Layer of cells

Smooth muscle

Connective tissue

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Your Heartbeat The action of the heart has two main phases. Inthe first phase, the heart relaxes and the atria fill with blood. In the secondphase, the heart contracts and pumps blood. First the atria contract,pumping blood into the ventricles. Then the ventricles contract, pump-ing blood into the large blood vessels going toward the lungs or towardthe rest of the body. The familiar lub-dub sound of a heartbeat occursduring the pumping phase. As the valves between the atria and ventriclesclose, the lub sound is made. The dub sound is heard when the valvesbetween the ventricles and large blood vessels close.

The rate at which your heart muscles contract is regulated by thea small group of cells in the wall of the right atrium. The

pacemaker receives messages from your brain to increase or decrease yourheart rate.

Average heart rate varies from one person to the next and from onesituation to the next. Your heart most likely beats about 70 to 80 times perminute when you are inactive. When you exercise, your heart speeds upin response to the body’s need for more oxygen and nutrients and toremove excess carbon dioxide.

Blood VesselsYour heart pumps blood through an extensive network of blood vessels.If all the blood vessels in your body were placed end to end, they couldwrap around Earth more than two times. The three main types of bloodvessels in your body are arteries, capillaries, and veins.

pacemaker,

FIGURE 2 Blood flows from theheart through arteries, capillaries,and then veins.

For: More on the heartVisit: PHSchool.comWeb Code: ctd-4121

PHSchool.com

and HealthDescriptive Writing

Have students describe the beating of theheart and what happens inside the heartas if they were writing to inform a middleschool student—that is, someone who haslittle detailed knowledge about the heart.Ask students to use terms from the chapter.Their descriptions should be clear and

detailed. This activity requires students todescribe the heart so thoroughly that anygaps or misconceptions in their knowledgewill be revealed to them as they write. Letstudents use their textbooks as needed tofill any gaps and correct any errors.

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Less Proficient ReadersUse a cycle diagram to show students howto organize the information about the flowof blood through the heart and the bloodvessels. Begin the diagram with the flow ofblood from the body into the right atrium.Blood then flows into the right ventricle,which pumps blood to the lungs. Bloodflows from the lungs into the left atrium,

then into the left ventricle, which pumpsblood through the aorta to the body. Theaorta branches into many smaller arteriesthat carry blood to all parts of the body.Blood flows from the arteries into the cap-illaries, then into small blood vessels thatjoin to form veins. Veins carry blood backto the right atrium.

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Building VocabularyHelp students remember the differencebetween arteries and veins by havingthem associate the phrase “away from”with arteries. Ask: Which type of bloodvessel carries blood away from theheart? (arteries) Point out that bothaway from and arteries start with theletter a.

Teacher DemoYou can show students which way bloodflows through veins with a visualdemonstration on your arm or on anarm of a student volunteer. The arm youuse must prominently show a blue veinon the forearm running from the wristto the elbow. As students observe, pressdown on the vein near the wrist. Whilepressing down with one hand, trace thevein’s path with a finger of your otherhand along the forearm to the elbow,gently applying pressure as you move upthe vein. The vein should disappear untilyou release the pressure on the veinnear the wrist. Ask: From what you’veobserved, what can you tell about thedirection the blood flows in this vessel?(The blood flows from the wrist towardthe elbow, because pressing down onthe vessel near the wrist stopped theflow of blood.) What stops the bloodfrom flowing back toward the wrist fromabove the elbow? (valves inside the vein)

Answers will vary. A healthyheart often beats 70 to 80

times a minute, though there is widevariation among individuals.

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Vein

Capillary

Single layer of cells

Layer of cells

Smooth muscle

Connective tissue

CapillaryCross Section

Vein Cross Section


Arteries Blood vessels that carry blood away from the heart are calledMost arteries carry oxygen-rich blood. The exceptions are the

arteries that carry oxygen-poor blood from the heart to the lungs.The largest artery in the body is the aorta (ay AWR tuh). Blood leaves

the left ventricle through the aorta, which branches into many smallerarteries that carry blood to your organs, muscles, and bones.

As you can see in Figure 2, arteries have thick walls that are bothstrong and flexible. When your ventricles contract, blood surges throughyour arteries, causing their elastic walls to expand and then relax. Thepulse you feel in your wrist occurs when an artery expands.

Capillaries Branching from the smallest arteries are thesmallest blood vessels in your body. As blood flows through the capillar-ies, oxygen and dissolved nutrients diffuse through the capillary walls andinto your body’s cells. At the same time, wastes from body cells, such ascarbon dioxide, diffuse into the blood. Capillaries also are involved intemperature regulation. When you are cold, the capillaries near the sur-face of your skin narrow and keep heat in your body. When you are warm,they expand and allow excess heat to escape your body.

Veins From the capillaries, blood flows into small blood vessels thatjoin together to form veins. are large, thin-walled blood vesselsthat carry blood to the heart. By the time blood reaches veins, the pump-ing force of the heart has little effect. Skeletal muscle contractions help tosqueeze blood back toward the heart. Valves inside the veins prevent bloodfrom flowing backward.

Locate the pulse in your wrist. How many timesdoes your pulse beat in one minute?


Veins

capillaries,

arteries.


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Cooperative Learning Ask a school nurse to demonstrate tothe class how a blood pressure readingis taken. The nurse’s presentationshould include an explanation of how a sphygmomanometer works and an explanation of systolic and diastolicreadings. Before the class visit, have students break into small groups. Eachgroup should brainstorm at least twoquestions about blood pressure to askthe nurse.

Building Health SkillsAdvocacy Have groups make posters to inform the public about what bloodpressure is, what blood pressure read-ings mean, what different ranges ofblood pressures indicate, and why people should have their blood pressure checked. The poster mayinclude drawings, cartoons, or otherimages that would catch a person’s eye.Encourage students to find places in thecommunity to display their posters withpermission.

Addressing MisconceptionsAge and Blood Pressure Many peoplethink of high blood pressure as a normalpart of the aging process. Explain thatblood pressure does not naturally rise asone gets older. Factors that contributeto high blood pressure include a poordiet, lack of exercise, and an increase inbody weight. Explain that there appearsto be a connection between hypertensionand age because years of poor healthhabits tend to catch up on people asthey age.

Allow students to answer this question in their

private journals.

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FIGURE 3 Blood pressure variesfrom person to person. Factorssuch as age, weight, fitness, andmood affect blood pressure.

Measuring Blood Pressure Visits to a doctor usually includehaving your blood pressure measured. is the force withwhich blood pushes against the walls of your blood vessels.

Figure 3 shows a sphygmomanometer (sfig moh muh NAHM uh tur),an instrument used to measure blood pressure. The healthcare providerpumps air into the cuff around the patient’s upper arm until a large arterypresses closed. As air is released from the cuff, the provider listens for thesound of flowing blood and records the reading from the sphygmo-manometer. This first reading represents the systolic pressure—thepressure caused when the heart’s ventricles contract. When the soundstops, the provider records the second reading. This second reading is thediastolic pressure—the pressure when the ventricles are relaxed.

Blood pressure readings are recorded as the systolic pressure over thediastolic pressure. For example, a person with a reading of 120/80 has asystolic pressure of 120 and a diastolic pressure of 80.

� Normal Blood Pressure Blood pressure readings vary from personto person. A blood pressure reading is considered normal if it fallswithin the range of 90/60 to 119/79.

� Low Blood Pressure Blood pressure lower than 90/60 is considered tobe low blood pressure. Doctors are not usually concerned if blood pres-sure is slightly low, unless symptoms indicate that organs are notreceiving enough oxygen. Causes of low blood pressure include medica-tions, dehydration, and allergic reactions.

� High Blood Pressure A person whose blood pressure is consistently140/90 or greater has high blood pressure, or Peoplewith a blood pressure between 120/80 and 139/89 have “prehyper-tension,” and are likely to develop hypertension in the future. You willread about the dangers of hypertension in Section 2.

When was the last time your blood pressure wasmeasured? What was the measurement?


hypertension.

Blood pressure

Blood Pressure REadingsReadings

Reading Condition(in millimeters of mercury)

Less than 90/60 Low blood pressure

90/60 to 119/79 Normal

120/80 to 139/89 Prehypertension

140/90 or greater Hypertension

FYI !FYI !Blood Pressure Near the HeartFor many years doctors have relied on bloodpressure readings from the upper arm totrack the effect of blood-pressure medicines.A recent study, however, revealed that someblood pressure medicines affect the pressurein the arm and the aorta differently. Withsome medicines although pressure in the

arm lowered, pressure in the aorta did not. With other medicines pressure in the aortalowered, although pressure in the arm didnot. Patients in the study who took medicinethat lowered blood pressure in the aorta, but not necessarily the arm, experiencedfewer heart attacks.



English Language LearnersHave students pronounce the word hyper-tension, and then discuss common usage ofthe word tension. The word can be used todescribe an emotional state or, as in thiscase, a physical property of a material. Toillustrate the concept of tension, stretch a

rubber band and point out that you areincreasing the tension on the rubber band.Explain that the prefix hyper- means “aboveand beyond” or “excessive.” Hypertensionis tension of the blood vessels over andbeyond what is healthy.

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Blood

Active LearningHave students use colored modeling clayto make models of the three differenttypes of blood cells. After they havecompleted their models, have studentsdraw and label a picture of each type of blood cell.

Cultural ConnectionPoint out that in different regions ofthe world some blood types are morecommon than others. The distributionof blood types in the United States is 45 percent type O, 40 percent type A,11 percent type B, and 4 percent typeAB. Meanwhile, in most parts of Centraland South America type A blood is veryrare. Many Americans do not know theirblood type. However, in Japan manypeople think that a person’s blood typeinfluences his or her personality.

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� Plasma

� Platelets

� Red blood cell

� White blood cell

BloodThe average adult has about 4 to 6 quarts of blood circulating throughhis or her blood vessels. Blood is a complex tissue that consists of cellsand cell pieces in a watery solution. The four components of blood areplasma, red blood cells, white blood cells, and platelets.

Plasma The liquid component of the blood is called Thisstraw-colored liquid makes up about 55 percent of the blood. Plasma ismostly water, with substances such as nutrients, hormones, and salts dis-solved in it. These substances are necessary for many processes that occurin cells. Plasma also carries waste products such as urea to the kidneys forremoval from the body.

Red Blood Cells The cells that carry oxygen from the lungs to all theparts of your body are Red blood cells contain hemo-globin, which is an iron-containing substance to which oxygen binds. Thereaction between oxygen and the iron in hemoglobin gives blood itsbright red color. Once oxygen has diffused to tissues, blood becomes adull red.

White Blood Cells Your body’s help protect youagainst diseases and foreign substances. They are larger than red bloodcells, but far less numerous. There are several kinds of white blood cells.Some white blood cells make chemicals that help your body resist diseasessuch as cancer. Others destroy invading microorganisms by surroundingand consuming them.

Platelets (PLAYT lits) are cell fragments that play an impor-tant role in the blood clotting process. When you get a cut, platelets stickto the edges of the cut and release proteins called clotting factors. Clottingfactors and other plasma proteins form a net of fibers across the cut. Thefibers trap more platelets and blood cells until a plug forms to seal the cut.When the plug dries, it forms a scab.

Platelets

white blood cells

red blood cells.

plasma.

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FIGURE 4 Blood consists of liquidplasma, red blood cells, whiteblood cells, and platelets.


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If You Have Blood Type

You Can Receive Blood Type(s)

A B AB O

A and O B and O A, B, AB, O and O

Safe Blood Transfusions

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Blood Types A person’s blood type is determined by the proteinspresent on the surface of the red blood cells. Depending on which pro-teins are present, a person’s blood type can be type A, B, AB, or O.

A second blood type is determined by the presence or absence of theRh factor protein. If your red blood cells have the Rh factor, your bloodis said to be Rh positive. If your red blood cells lack the Rh factor, yourblood is Rh negative. About 85 percent of people are Rh positive.

Transfusions After an injury, surgery, or some illnesses, a personmay require a blood transfusion. During a transfusion, blood from adonor is transferred to the patient’s bloodstream. Donated blood is testedto identify the blood type. It is also screened for the presence of somemicroorganisms such as those that cause hepatitis or AIDS.

Why is blood type important? If a patient is given the wrong bloodtype during a transfusion, the blood will clump together in the patient’sblood vessels. This is a life-threatening reaction. Figure 5 shows whichblood types can be given safely during a transfusion.

Section 1 Review

Key Ideas and Vocabulary1. List the three main functions of the cardiovascular

system.

2. Describe the pathway of blood through your heartstarting at the right atrium.

3. List the three types of blood vessels in the order inwhich they receive blood from the heart.

4. Name the four components of blood and their rolein the body.

Critical Thinking5. Applying Concepts What is the function of a

closed heart valve?

6. Predicting How might low levels of iron affect theblood’s ability to transport oxygen?

7. Evaluating Why are people with blood type Ocalled “universal donors”? Why are people withblood type AB called “universal recipients”?

FIGURE 5 If you ever need atransfusion, your blood type will bechecked to make sure you receivethe correct blood.Reading Tables If you have bloodtype A, what blood type(s) couldyou safely receive?

CommunityHealth and

Blood Drive Contact your local chapter of theAmerican Red Cross to find out about upcomingblood drives in your community. With theirguidance, prepare a fact sheet describing therequirements for and the importance of donatingblood. Get permission to display the fact sheetand a list of local blood drives in a communitybuilding or your school.

3. AssessEvaluateThese assignments can help you assessstudents’ mastery of the section content.

Section 1 ReviewAnswers appear below.

Teaching Resources• Practice 12-1• Section 12-1 Quiz

ReteachList the section’s vocabulary terms onthe board. Point to each word and havestudents brainstorm facts about thatterm. Record the key facts. For termsthat students know little about, havethem reread relevant passages. Suggestthat students record the facts for eachterm in their notebooks.

Enrich

Teaching Resources• Enrich 12-1

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3. arteries, capillaries, veins

4. Plasma: transports many necessary sub-stances and wastes. Red blood cells: carryoxygen. White blood cells: protect the bodyfrom disease and foreign substances.Platelets: help in the clotting process.

5. A closed heart valve prevents blood fromflowing in the wrong direction.

6. Iron is needed to make hemoglobin—thesubstance that transports oxygen.

7. Anyone can receive blood type O. Peoplewith blood type AB can receive all types.

1. delivering materials, removingwastes, and fighting disease

2. Blood flows from the right atriuminto the right ventricle, through thelungs, into the left atrium, and intothe left ventricle.

Section 1 Review

Blood Drive You may want to dividethe class into small groups for thisactivity and have each group produceits own fact sheet and list of localblood drives.

Health and Community

Visual Learning: Figure 5Have students examine the table aboutsafe blood transfusions. Ask: If a patienthas blood type B, what blood types canthat patient safely be given in a trans-fusion? (type B or type O) What wouldhappen if that patient were givenblood type A? (The blood would clumptogether in the patient’s blood vessels.)Caption Answer blood types A and O

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Documents

Section 1 Your Cardiovascular Systemcardiovascular system, or the circulatory system, consists of your heart, blood vessels, and blood.The main functions of the cardiovascular system