37–1 The Circulatory System Section 37–1

1 Key Concepts What are the structures of thecirculatory System ? What are the three types ofblood vessels in the circulatorysystem?Vocabularymyocardiumat riumventriclepulmonary circulationsystemic circulationvalvepacemakeraortaarterycapi llary veinatherosclerosisReading Strategy: Using VisualsBefore youread, preview Figure 37 a list of questions aboutthe illustration. As you read,write down the answers to thequestions. Figure 37 1 These roads forma transportation System . UsingAnalogiesHow is the humancirculatory System like the streets and highways of a large city?Your heartbeat is a sign of life itself. Even when you drift offto sleep, your heart continues to beat at a steady is this process so important that it must keep going evenwhen you sleep? Each breath you take brings air into your respiratory sys-tem. The oxygen in that air is needed by the trillions of cells in your body. Your heart is essential in delivering that oxygen.

2 Itsbeating produces the force to move oxygen-rich blood throughthe Circulatory System . Interrelationships between the circula-tory and respiratory systems supply cells throughout the bodywith the nutrients and oxygen they need to stay of the Circulatory SystemOrganisms composed of a small number of cells do not need acirculatory System . Most cells in such organisms are in directcontact with the environment. Oxygen, nutrients, and wasteproducts can easily diffuse back and forth across cell organisms, however, cannot rely on diffusion. Most oftheir cells are not in direct contact with the environment, andsubstances made in one part of the organism may be needed inanother part. In a way, this same problem is faced by the mil-lions of people living in a large city. Cities have transportationsystems that move people, goods, and waste material from one place to another. The transportation System of a city is itsstreets, highways, and rail lines.

3 The transportation System of a living organism is its Circulatory and other vertebrates have closed circulatorysystems. This means that a circulating fluid called blood iscontained within a System of human Circulatory System consists of the heart, a series of blood vessels, and the blood that flows through 1 The Circulatory System1 functions of thehuman Circulatory structures ofthe Circulatory three types ofblood vessels in the circula-tory PreviewExplain that the Circulatory systemconsists of the heart and blood ves-sels. Then, call students attention tothe vocabulary words and ask:Which words refer to structures ofthe heart, and which words referto types of blood vessels?(Myocardium, atrium, ventricle, valve,aorta, and pacemaker refer to struc-tures of the heart. Artery, capillary, andvein refer to types of blood vessels.)Reading StrategyHave students write the headingsand subheadings in outline form.

4 Asthey read, have them fill in the out-line with enough details to makeeach topic clear and INSTRUCTF unctions of theCirculatory SystemBuild Science SkillsCalculatingHelp students appreci-ate how much blood is pumpedthrough the Circulatory System . Tellthem that the heart pumps an aver-age of about 5 L of blood perminute. Ask: How many liters ofblood are pumped through the cir-culatory System in an averagelifespan of 75 years?(Almost200,000,000 L) Section 37 1 Circulatory and respiratory Systems943 Answer to .. Figure 37 1 Blood vessels are likethe streets and highways that carrymaterials to each part of a city. Section RESOURCESP rint: Laboratory Manual B,Chapter 37 Lab Teaching Resources,Lesson Plan 37 1,Adapted Section Summary 37 1, AdaptedWorksheets 37 1, Section Summary 37 1,Worksheets 37 1, Section Review 37 1,Enrichment Reading and Study Workbook A, Section 37 1 Adapted Reading and Study Workbook B, Section 37 1 Probeware Lab Manual,What factors affectheart rate?

5 Technology: iText, Section 37 1 Animated Biological Concepts DVD,43 Human Circulation Transparencies Plus, Section 37 1 Lab Simulations CD-ROM,Cardiovascular 1:The Beating Heart Virtual Labs,Lab 20 TimeSaver0942_0963_bi_c07_te 3/13/06 2:57 PM Page 943 Aortic ValvePrevents blood from flowing back into the left ventricle after it has entered the aortaSuperior Vena CavaLarge vein that brings oxygen-poor blood from the upper part of the body to the right atriumRight AtriumTricuspid ValvePrevents blood from flowing back into the right atrium after it has entered the right ventricleRight VentricleInferior Vena CavaVein that brings oxygen-poor blood from the lower part of the body to the right atriumAortaBrings oxygen-rich blood from the left ventricle to the bodyPulmonary ArteriesBring oxygen-poor bloodto the right or left lungPulmonary VeinsBring oxygen-rich bloodfrom each of the lungs to the left atriumLeft AtriumMitral ValvePrevents blood from flowing back into the left atrium after it hasentered the left ventricleLeft VentricleSeptumPulmonary ValvePrevents blood fromflowing back into theright ventricle after ithas entered thepulmonary arteryThe

6 HeartAs you can feel with your hand, your heart is located near thecenter of your chest. The heart, shown in Figure 37 2,which iscomposed almost entirely of muscle, is a hollow organ that isabout the size of your clenched fist. The heart is enclosed in aprotective sac of tissue called the pericardium (pehr-ih-KAHR-dee-um). In the walls of the heart, there are two thin layers ofepithelial and connective tissue that form a sandwich around athick layer of muscle called the The powerfulcontractions of the myocardium pump blood through the cir-culatory 37 2 The Circulatory System consists of the heart, a series of blood vessels,and the the valves between the atria and ventricles and those between theventricles and the blood vessels leaving the heart. The valves prevent blood from OF THEHEARTFor:The Heart Code:cbp-0371944 Chapter 37 The HeartDemonstrationDisplay a three-dimensional model ofthe heart that can be taken apart toshow the inside.

7 Call on students toidentify each part of the heartdescribed in the text, including theseptum, atria, and ventricles. Havestudents trace the route of bloodthrough the heart. Point out thevalves, and explain how they letblood flow in only one direction. Use VisualsFigure 37 2 Help students under-stand how blood flows through theheart. Explain that blood alwaysleaves the heart through arteries andalways returns to the heart throughveins. Check students understandingof how the heart pumps blood byasking: Where is blood pumped bythe atria?(To the ventricles)Where isblood pumped by the ventricles?(To the lungs and the rest of the body)Inclusion/Special NeedsUse a hands-on experience tohelp students appreciate thework of the heart. Have themsqueeze a tennis ball once persecond for two minutes with-out stopping. As they do,explain that this is how hardthe heart works. Stress that theheart continues to work thisway nonstop for life.

8 Less Proficient ReadersHelp students understand thedifferent types of blood vesselsby having them make a graphic organizer, such as acompare/contrast table orVenn diagram, to summarizethe similarities and differencesamong the three LearnersHave students who need anextra challenge learn aboutheart valve defects. Theyshould investigate types ofdefects and their causes, howthey affect health, and whetherthey can be repaired students to share whatthey learn in an oral 1 (continued)For:The Heart Code:cbe-0371 Students learn the parts of theheart and see the flow of bloodthrough the ACCESS0942_0963_bi_c07_te 3/13/06 2:57 PM Page 944 The heart muscle contracts on average 72 times a minute, pumping about 70 milliliters of bloodwith each contraction. This means that during oneyear, an average person s heart pumps more thanenough blood to fill an Olympic-sized swimmingpool. (An Olympic-sized swimming pool is about2,000,000 liters: liters 4320 beats per hour 24 hours 365 days = 2,649,024 liters.)

9 Dividing the right side of the heart from the leftside of the heart is the septum. The septum preventsthe mixing of oxygen-poor and oxygen-rich blood. Oneach side of the septum are two chambers. The upperchamber, which receives the blood, is the (plural: atria). The lower chamber, which pumpsblood out of the heart, is the The hearthas four chambers in total two atria and Through the BodyThe heartfunctions as two separate 37 3 shows the circulation of blood through the right side of the heart pumps blood from theheart to the lungs. This pathway is known asIn the lungs, carbondioxide leaves the blood and oxygen is oxygen-rich blood then flows into the left side of the heart and is pumped to the rest of the pathway is calledBlood that returns to the right side of the heart isoxygen-poor because cells have absorbed much ofthe oxygen and loaded the blood with carbondioxide. At this point, it is ready for another trip tothe Through the HeartBlood enters the heartthrough the right and left atria.

10 As the heart contracts, bloodflows into the ventricles and then out from the ventricles toeither the body or the lungs. There are flaps of connectivetissue called between the atria and the moving from the atria holds the valves open. When theventricles contract, the valves close, which prevents blood fromflowing back into the the exits from the right and left ventricles, there arevalves that prevent blood that flows out of the heart fromflowing back in. This System of valves keeps blood movingthrough the heart in one direction, like traffic on a one-waystreet. The one-way flow increases the pumping efficiency of the heart. The valves are so important to heart function thatsurgeons often attempt to repair or replace a valve that hasbeen damaged due to is the function of the heart valves?valvessystemic cavaInferiorvena cavaAortaCapillaries ofabdominal organsand legsCapillariesof left lungCapillaries ofhead and armsPulmonaryarteryPulmonaryveinCapillar iesof right lung Figure 37 3 The Circulatory System is divided intotwo pathways.