Anatomy and Physiology of the Cardiovascular System

Chapter © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC 5 NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Anatomy© Jonesand & Physiology Bartlett Learning, LLC of © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION the Cardiovascular System

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION OUTLINE Aortic arch: The second section of the aorta; it branches into Introduction the brachiocephalic trunk, left common carotid artery, and The Heart left subclavian artery. Structures of the Heart Aortic valve: Located at the base of the aorta, the aortic Conduction System© Jones & Bartlett Learning, LLCvalve has three cusps and opens© Jonesto allow blood & Bartlett to leave the Learning, LLC Functions of the HeartNOT FOR SALE OR DISTRIBUTIONleft ventricle during contraction.NOT FOR SALE OR DISTRIBUTION The Blood Vessels and Circulation Arteries: Elastic vessels able to carry blood away from the Blood Vessels heart under high pressure. Blood Pressure Arterioles: Subdivisions of arteries; they are thinner and have Blood Circulation muscles that are innervated by the sympathetic nervous Summary© Jones & Bartlett Learning, LLC system. © Jones & Bartlett Learning, LLC Atria: The upper chambers of the heart; they receive blood CriticalNOT Thinking FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Websites returning to the heart. Review Questions Atrioventricular node (AV node): A mass of specialized tissue located in the inferior interatrial septum beneath OBJECTIVES the endocardium; it provides the only normal conduction pathway between the atrial and ventricular syncytia. After reading this chapter, readers should be able to: © Jones & Bartlett Learning, LLC © JonesAV bundle: & Bartlett The bundle Learning, of His; a large LLCstructure that receives 1. Describe the organization of the cardiovascular the cardiac impulse from the distal AV node. It enters the NOT FOR SALEsystem OR DISTRIBUTIONand the heart. NOT FOR SALE OR DISTRIBUTION upper part of the interventricular septum. 2. Identify the layers of the heart wall. Blood volume: The sum of formed elements and plasma 3. Describe the general features of the heart. volumes in the vascular system; most adults have about 5 L 4. Answer the question of why the left ventricle is of blood. more muscular than the right ventricle. Capillaries: The smallest-diameter blood vessels, which 5. Describe the components© Jones and & Bartlettfunctions of Learning, the LLC © Jones & Bartlett Learning, LLC connect the smallest arterioles to the smallest venules. conducting systemNOT of FORthe heart. SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Cardiac conduction system: The initiation and distribution 6. Explain the events of the cardiac cycle. of impulses through the myocardium that coordinates the 7. Define cardiac output and stroke volume. cardiac cycle. 8. Distinguish among the types of blood vessels, their Cardiac cycle: A heartbeat; it consists of a complete series structures, and their functions. of systolic and diastolic events. 9.© JonesIdentify the & majorBartlett arteries Learning, and veins ofLLC the © Jones & Bartlett Learning, LLC Cardiac output: The volume discharged from the ventricle NOTpulmonary FOR SALEcircuit as OR well DISTRIBUTIONas the areas they serve. NOT FOR SALE OR DISTRIBUTION per minute, calculated by multiplying stroke volume by heart 10. Describe the hepatic portal system. rate, in beats per minute. Cardiac veins: Those veins that branch out and drain blood KEY TERMS from the myocardial capillaries to join the coronary sinus. © Jones & Aorta:Bartlett The largest Learning, artery in theLLC body, the aorta originates © JonesCarotid & sinuses: Bartlett Enlargements Learning, near theLLC base of the carotid from the left ventricle of the heart and extends down to the arteries that contain baroreceptors and help to control blood NOT FOR SALEabdomen, OR where DISTRIBUTION it branches off. NOT FORpressure. SALE OR DISTRIBUTION

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© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEKEY TERMS OR DISTRIBUTION continued NOTPulmonary FOR SALE valve: OR Lying DISTRIBUTION at the base of the pulmonary trunk, Cerebral arterial circle: The circle of Willis; it connects the this valve has three cusps and allows blood to leave the vertebral artery and internal carotid artery systems. right ventricle while preventing backflow into the ventricular Chordae tendineae: Strong fibers originating from the chamber. papillary muscles that attach to the cusps of the tricuspid Purkinje fibers: Consisting of branches of the AV bundle valve. © Jones & Bartlett Learning, LLCthat spread and enlarge, these© fibers Jones are located & Bartlett near the Learning, LLC papillary muscles; they continue to the heart’s apex and Coronary arteries: TheNOT first FORtwo aortic SALE branches, OR whichDISTRIBUTION NOT FOR SALE OR DISTRIBUTION supply blood to the heart tissues. cause the ventricular walls to contract in a twisting motion. Coronary sinus: An enlarged vein joining the cardiac veins; it Septum: A solid, wall-like structure that separates the left atria empties into the right atrium. and ventricle from the right atria and ventricle. Diastole: The relaxation of a heart structure. Sinoatrial node (SA node): A small mass of specialized Diastolic pressure: The lowest pressure that remains in the tissue just beneath the epicardium in the right atrium that © Jones & Bartlett Learning, LLC initiates impulses© Jones through & the Bartlett myocardium Learning, to stimulate LLC arteriesNOT beforeFOR the SALE next ventricular OR DISTRIBUTION contraction. NOT FOR SALE OR DISTRIBUTION Electrocardiogram (EKG): The recording of electrical contraction of cardiac muscle fibers. changes in the myocardium during the cardiac cycle. The Stroke volume: The volume of blood discharged from the EKG machine works by placing nodes on the skin that ventricle with each contraction; it is usually about 70 mL. connect via wires and respond to weak electrical changes Superior vena cava: Along with the inferior vena cava, one of the two largest veins in the body; the superior vena cava is © Jones & Bartlettof the heart. Learning, The abbreviation LLC EKG is more commonly used © Jones & Bartlett Learning, LLC than ECG. formed by the joining of the brachiocephalic veins. NOT FOR SALEEndocardium: OR DISTRIBUTION The inner layer of the heart wall. NOTSystemic FOR SALE circuit: ORThe arteriesDISTRIBUTION and arterioles, which send Epicardium: The outer layer of the heart wall. oxygenated blood and nutrients to the body cells while Functional syncytium: A mass of merging cells that functions removing wastes. as a unit. Systole: The contraction of a heart structure. Hepatic portal system: The veins that drain the abdominal Systolic pressure: The maximum pressuring during ventricular viscera, originating in© the Jones stomach, & intestines, Bartlett pancreas, Learning, and LLCcontraction. © Jones & Bartlett Learning, LLC spleen, to carry bloodNOT through FOR a hepatic SALE portal OR vein DISTRIBUTIONto the Thyrocervical arteries: Those NOTthat branch FOR off SALEto the thyroid OR DISTRIBUTION liver. and parathyroid glands, larynx, trachea, esophagus, pharynx, Inferior vena cava: Along with the superior vena cava, one of and muscles of the neck, shoulder, and back. the two largest veins in the body; it is formed by the joining Tricuspid valve: Lying between the right atrium and ventricle, of the common iliac veins. this valve allows blood to move from the right atrium into the Mitral© Jonesvalve: The & bicuspid Bartlett valve; Learning, it lies between LLC the left atrium right ventricle© Jones while preventing & Bartlett backflow. Learning, LLC Vasoconstriction: The contraction of blood vessels, which andNOT left ventricle,FOR SALE preventing OR blood DISTRIBUTION from flowing back into NOT FOR SALE OR DISTRIBUTION the left atrium from the ventricle. reduces their diameter. Myocardium: The thick middle layer of the heart wall that is Vasodilation: The relaxation of blood vessels, which increases mostly made of cardiac tissue. their diameter. Pacemaker: The term used to refer to the sinoatrial node (SA Veins: Blood vessels that carry blood back to the atria; they are less elastic than arteries. © Jones & Bartlettnode). Learning, LLC © Jones & Bartlett Learning, LLC Papillary muscles: Those muscles that contract as the Ventricles: The lower chambers of the heart; they receive NOT FOR SALEheart’s OR ventricles DISTRIBUTION contract, pulling on the chordae tendineaeNOT FORblood fromSALE the atria,OR whichDISTRIBUTION they pump out into the arteries. to prevent the cusps from swinging back into the atrium. Venules: Microscopic vessels that link capillaries to veins. Pericardium: A membranous structure that encloses the Vertebral arteries: One of the main divisions of the heart and proximal ends of the large blood vessels and that subclavian and common carotid arteries; the vertebral consists of double layers. arteries run upward through the cervical vertebrae into the Peripheral resistance:© A Jones force produced & Bartlett by friction Learning, between LLCskull and supply blood to the vertebrae,© Jones their & ligaments, Bartlett and Learning, LLC blood and blood vesselNOT walls. FOR SALE OR DISTRIBUTIONtheir muscles. NOT FOR SALE OR DISTRIBUTION Pulmonary circuit: The venules and veins, which send Viscosity: Thickness or stickiness; the resistance of fluid to deoxygenated blood to the lungs to receive oxygen and flow. In a biologic fluid, viscosity is caused by the attraction unload carbon dioxide. of cells to one another. © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Introduction Approximately 7,000 L of blood is pumped by the heart every day. In an average person’s life, the heart will contract about The human heart pumps blood through the arteries, which 2.5 billion times. connect to smaller arterioles and then even smaller capil- Blood flow throughout the body begins its return to the laries. It is here that nutrients, electrolytes, dissolved gases, heart when the capillaries return blood to the venules and © Jones & andBartlett waste products Learning, are exchanged LLC between the blood and© Jonesthen to & the Bartlett larger veins. Learning, The cardiovascular LLC system, there- NOT FOR SALEsurrounding OR tissues.DISTRIBUTION The capillaries are thin-walled vesselsNOT fore, FOR consists SALE of a closedOR DISTRIBUTION circuit: the heart, arteries, arterioles, interconnected with the smallest arteries and smallest veins. capillaries, venules, and veins (see Figure 5–1). The venules © Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION

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Subclavian artery Jugular vein © Jones & Bartlett Learning, LLC © JonesCapillary & Bartlett beds of Learning, LLC Carotid artery Subclavian lungs where gas NOT FOR SALE OR DISTRIBUTIONvein NOT FORexchange SALE occurs OR DISTRIBUTION Superior Pulmonary arteries vena cava Aorta

Inferior Pulmonary Pulmonary circuit vena© cava Jones & Bartlett Learning, LLC artery © Jones & Bartlett Learning, LLC

RenalNOT artery FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTIONPulmonary veins Renal vein Hepatic

vein Vena Pulmonary circulation cavae Aorta Aorta and branches © Jones & Bartlett Learning, LLC ©Mesenteric Jones & Bartlett Learning, LLC Common veins NOT FOR SALEiliac vein OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Mesenteric arteries

Right Left ventricle ventricle © Jones & Bartlett Learning, LLC Systemic ©circuit Jones & Bartlett Learning, LLC Common iliac artery NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Femoral artery

Arterioles Systemic circulation Femoral © Jones & Bartlett Learning, LLC vein © Jones & Bartlett Learning, LLC Capillary beds of NOT FOR SALE OR DISTRIBUTION NOT FOR SALE ORall DISTRIBUTION body tissues where gas Venules exchange occurs Great saphenous Oxygen-poor, Oxygen-rich, vein CO2-rich blood CO2-poor blood © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC (b) NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Figure 5–1 The circulatory system. (a) The circulatory system consists of a series of vessels that transport blood to and from the heart, the pump. (b) The circulatory system has two major circuits: the pulmonary circuit, which transports blood to and from the lungs, and the systemic circuit, which transports blood to and from the body (excluding the lungs). © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

pulmonary circuit and veins are part of the because they The Heart send deoxygenated blood to the lungs to receive oxygen and unload carbon dioxide. The arteries and arterioles are part The human heart is a muscular organ containing four cham- © Jones & ofBartlett the systemic Learning, circuit because LLC they send oxygenated blood© Jonesbers that & isBartlett situated just Learning, to the left of LLC the midline of the tho- NOT FOR SALEand nutrients OR DISTRIBUTIONto the body cells while removing wastes. AllNOT racic FOR cavity. SALE It is ORapproximately DISTRIBUTION the size of a man’s closed body tissues require circulation to survive. fist. The upper two chambers (atria) are divided by a wall- © Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION

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© Jones &like Bartlett structure Learning, called the interatrial LLC septum. The lower two© JonesAn average& Bartlett adult has Learning, a heart that LLCis about 14 cm long by 9 ventricles chambers ( ) are divided by a similar structure calledNOT cm FOR wide. SALE The base OR of the DISTRIBUTION heart is actually the upper portion, NOT FOR SALEthe interventricular OR DISTRIBUTION septum. Between each atrium and ven- where it is attached to several large blood vessels. This por- tricle, valves allow blood to flow in one direction, prevent- tion lies beneath the second rib. The distal end of the heart ing backflow. extends downward, to the left, ending in a blunt point called Blood flow through the heart is shown in Figure 5–2. the apex, which is even with the fifth intercostal space. Blood that is low in oxygen© Jones flows into& Bartlett the right atrium Learning, from LLCThe three layers comprising© the Jones wall of the& Bartlettheart are the Learning, LLC the veins known as the superior vena cava and inferior vena outer pericardium, middle myocardium, and inner endocar- cava. The superior venaNOT cava FOR carries SALE blood fromOR theDISTRIBUTION head, dium (see Figure 5–2). The pericardiumNOT FOR consists SALE of connec OR -DISTRIBUTION neck, chest, and arms. The inferior vena cava carries blood tive tissue and some deep adipose tissue, and it protects the from the remainder of the trunk and the legs. Blood in the heart by reducing friction. The thick myocardium is mostly right atrium then flows through the right atrioventricular (tri- made of cardiac muscle tissue that is organized in planes cuspid) valve into the right ventricle. From here it begins the and richly supplied by blood capillaries, lymph capillaries, pulmonary© Jones circuit &, withBartlett deoxygenated Learning, blood flowing LLC into the and nerve fibers.© Jones It pumps & blood Bartlett out of Learning,the chambers ofLLC the rightNOT and left FOR pulmonary SALE arteries OR DISTRIBUTIONand their smaller branches. heart. The endocardiumNOT FOR is SALEmade up OR of epithelium DISTRIBUTION and con- The blood becomes oxygenated while moving through the nective tissue with many elastic and collagenous fibers. It also lungs’ capillary beds. Also in this part of the system, carbon contains blood vessels and specialized cardiac muscle fibers dioxide is released. known as Purkinje fibers. The inside of the heart is divided into four hollow cham- © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Structures of the Heart bers, with two on the left and two on the right. The upper NOT FOR SALE OR DISTRIBUTION NOTchambers FOR SALE are called OR atria DISTRIBUTION and receive blood returning to the The heart lies inside the thoracic cavity, resting on the dia- heart. They have auricles, which are small projections that phragm. It is hollow and cone-shaped, varying in size. The extend anteriorly. The lower chambers are called ventricles heart is within the mediastinum in between the lungs. Its and receive blood from the atria, which they pump out into posterior border is near the vertebral column, and its ante- the arteries (see Figure 5–2). The left atria and ventricle are rior border is near the© sternum. Jones & Bartlett Learning, LLCseparated from the right atria ©and Jones ventricle & by Bartlett a solid wall- Learning, LLC septum NOT FOR SALE OR DISTRIBUTION like structureNOT (FOR SALE). This keepsOR DISTRIBUTION blood from one side of the heart from Superior vena cava (from head) Aorta mixing with blood from the other side (except in a developing fetus). The Right atrioventricular valve (AV valve), pulmonary Left pulmonary which consists of the mitral valve on © arteryJones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC artery the left and the tricuspid valve on NOT FOR SALE OR DISTRIBUTION NOT FORthe right,SALE ensures OR one-wayDISTRIBUTION blood flow Right between the atria and ventricles. pulmonary Left pulmonary The right atrium receives blood vein vein from two large veins called the superior vena cava and the inferior vena © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC cor- Left atrium cava as well as a smaller vein (the NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTIONonary sinus), which drains blood into Right atrium the right atrium from the heart’s myocardium. The tricuspid valve has projections (cusps) and lies between the right atrium and ventricle. This valve © Jones & Bartlett Learning, LLC allows blood© Jones to move & from Bartlett the right Learning, LLC Inferior vena atrium into the right ventricle while cava (from body) NOT FOR SALE OR DISTRIBUTIONInterventricular NOT FOR SALE OR DISTRIBUTION septum preventing backflow. The cusps of the tricuspid valve are attached to strong fibers called chordae tendineae, Right ventricle papillary Left ventricle which originate from small © Jones & Bartlett Learning, LLC © Jonesmuscles & Bartlett that project Learning, inward from LLC the Endocardium Pericardium ventricle walls. These muscles con- NOT FOR SALE OR DISTRIBUTION NOT FORtract SALE as the ventricle OR DISTRIBUTION contracts. When Myocardium the tricuspid valve closes, they pull on the chordae tendineae to prevent Figure 5–2 Blood flow through the heart. Deoxygenated (carbon-dioxide-enriched) blood (blue arrows) flows into the right atrium from the systemic circulation and is pumped into the right the cusps from swinging back into © Jones & ventricle.Bartlett The bloodLearning, is then pumped LLC from the right ventricle into the ©pulmonary Jones artery, & whichBartlett Learning,the atrium. LLC delivers it to the lungs. In the lungs, the blood releases its carbon dioxide and absorbs oxygen. The right ventricle’s muscular wall NOT FOR SALEReoxygenated OR blood DISTRIBUTION (red arrows) is returned to the left atrium, then NOTflows into FOR the left SALE ventricle, OR DISTRIBUTIONis thinner than that of the left ven- which pumps it to the rest of the body through the systemic circuit. tricle, as it only pumps blood to the © Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION

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lungs with a low resistance to blood flow. The Right © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Aorta left ventricle is thicker because it must force pulmonary arteries NOT FOR SALEblood to OR all body DISTRIBUTION parts, with a much higher NOT FOR SALE OR DISTRIBUTION resistance to blood flow. As the right ventricle Left pulmonary Superior arteries contracts, its blood increases in pressure to vena cava passively close the tricuspid valve. Therefore, Right this blood can only exit© through Jones the & pulmonary Bartlett Learning, LLC © Jones & Bartlett Learning, LLC trunk, which divides into the left and right pul- pulmonary Left pulmonary veins veins monary arteries that NOTsupply FORthe lungs. SALE At the OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION pulmonary valve trunk’s base, there is a with Right atrium three cusps that allow blood to leave the right Left atrium ventricle while preventing backflow into the Right atrio- Left atrioventricular chamber (see Figure 5–3). ventricular ventricular Four© Jones pulmonary & Bartlett veins (two Learning, from each of LLC (tricuspid) © Jones & Bartlett Learning,(tricuspid) LLC the NOTlungs) FORsupply SALEthe left atriumOR DISTRIBUTION with blood. valve NOT FOR SALE OR DISTRIBUTIONvalve Blood passes from the left atrium into the left ventricle through the mitral valve (bicuspid Inferior vena cava (from body) valve), preventing blood from flowing back into the left atrium from the ventricle. Like Semilunar valves © Jones & theBartlett tricuspid Learning, valve, the papillary LLC muscles and Chordae© Jones tendineae & Bartlett Learning, LLC chordae tendineae prevent the mitral valve’s NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Left ventricle cusps from swinging back into the left atrium Right ventricle when the ventricle contracts. The mitral valve (a) Septum closes passively, directing blood through the large artery known as the aorta. At the base of the aorta© Jones is the aortic & Bartlett valve, Learning, LLC © Jones & Bartlett Learning, LLC with three cusps. ThisNOT valve FOR opens SALE to allow OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION blood to leave the left ventricle during contraction. When the ventricle relaxes, the valve closes to prevent blood from backing up into the ventricle. The mitral and tricuspid valves are© known Jones as atrioventricular & Bartlett Learning,valves because LLC © Jones & Bartlett Learning, LLC they lie between the atria and ventricles. The pulmonaryNOT FOR and aortic SALE valves OR have DISTRIBUTION “half-moon” NOT FOR SALE OR DISTRIBUTION shapes and are therefore referred to as semilunar valves. Table 5–1 summarizes the various heart valves. The right atrium receives low-oxygen blood © Jones & throughBartlett the Learning,vena cava and LLCcoronary sinus. As (b) © Jones & Bartlett Learning, LLC NOT FOR SALEthe right OR atrium DISTRIBUTION contracts, the blood passes Figure 5–3NOT Heart FOR valves. SALE (a) A cross-section OR DISTRIBUTION of the heart showing the four through the tricuspid valve into the right ven- chambers and the location of the major vessels and valves. (b) Photograph of tricle (see Figure 5–3). As the right ventricle chordae tendineae. contracts, the tricuspid valve closes. Blood moves through the pulmonary valve into the The left atrium contracts, moving blood through the pulmonary trunk and ©pulmonary Jones arteries.& Bartlett It then Learning, enters the LLCmitral valve into the left ventricle.© Jones When the& Bartlettleft ventricle Learning, LLC capillaries of the alveoliNOT of the FOR lungs, SALE where ORgas exchanges DISTRIBUTION contracts, the mitral valve closes.NOT Blood FOR moves SALE through OR the DISTRIBUTION occur. This freshly oxygenated blood then returns to the heart aortic valve into the aorta and its branches. The first two aor- through the pulmonary veins, into the left atrium. tic branches are called the right and left coronary arteries.

■■Table 5–1 The Heart Valves Heart© Jones Valve & BartlettLocation Learning, LLC Action © Jones & Bartlett Learning, LLC TricuspidNOT valveFOR SALEBetween OR rightDISTRIBUTION atrium and right ventricle During ventricular NOTcontraction, FOR it prevents SALE blood OR from DISTRIBUTION moving from right ventricle into right atrium. Pulmonary valve At entrance to pulmonary trunk During ventricular relaxation, it prevents blood from moving from pulmonary trunk into right ventricle. Mitral (bicuspid) valve Between left atrium and left ventricle During ventricular contraction, it prevents blood from moving from left © Jones & Bartlett Learning, LLC © Jonesventricle &into Bartlett left atrium. Learning, LLC NOT FOR SALEAortic valve OR DISTRIBUTIONAt entrance to aorta NOTDuring FOR ventricular SALE relaxation, OR it DISTRIBUTIONprevents blood from moving from aorta into left ventricle.

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© Jones &They Bartlett supply Learning,blood to the heart LLC tissues, with openings lying© Jonesalmost & simultaneously. Bartlett Learning, The impulse LLC passes along junctional just beyond the aortic valve. NOTfibers FOR of SALEthe conduction OR DISTRIBUTION system to a mass of specialized tis- NOT FOR SALEThe bodyOR tissuesDISTRIBUTION require continual beating of the heart sue called the atrioventricular node (AV node), located in because they need freshly oxygenated blood to survive. Coro- the inferior interatrial septum, beneath the endocardium. nary artery branches supply many capillaries in the myocar- The AV node provides the only normal conduction pathway dium. These arteries have smaller branches with connections between the atrial and ventricular syncytia. Impulses are called anastomoses between© Jones vessels & providing Bartlett alternate Learning, blood LLCslightly delayed due to the small© diameterJones of& theBartlett junctional Learning, LLC pathways (collateral circulation). These pathways may supply fibers. The atria, therefore, have more time to contract and oxygen and nutrients toNOT the myocardium FOR SALE when OR blockage DISTRIBUTION of a empty all of their blood into theNOT ventricles FOR before SALE ventricular OR DISTRIBUTION coronary artery occurs. Branches of the cardiac veins drain contraction occurs. blood from the myocardial capillaries, joining an enlarged vein, When the cardiac impulse reaches the distal AV node, the coronary sinus, which empties into the right atrium. it passes into a large AV bundle (bundle of His), entering Conduction System the upper part of the interventricular septum. Nearly half- © Jones & Bartlett Learning, LLC way down the© septum,Jones these & Bartlett branches spreadLearning, into enlarged LLC StrandsNOT and FOR clumps SALE of specialized OR DISTRIBUTION cardiac muscle contain Purkinje fibers,NOT extending FOR SALEinto the papillaryOR DISTRIBUTION muscles. They only a few myofibrils and are located throughout the heart. continue to the heart’s apex, curving around the ventricles These areas initiate and distribute impulses through the myo- and passing over their lateral walls. The Purkinje fibers have cardium, comprising the cardiac conduction system that numerous small branches that become continuous with car- coordinates the cardiac cycle (see Figure 5–4). The sinoa- diac muscle fibers and irregular whorls. Purkinje fiber stimu- © Jones & trialBartlett node (SA Learning, node) is a small LLC mass of specialized tissue just© Joneslation causes& Bartlett the ventricular Learning, walls toLLC contract in a twisting NOT FOR SALEbeneath theOR epicardium DISTRIBUTION, in the right atrium. It is located nearNOT motion, FOR SALEto force bloodOR DISTRIBUTIONinto the aorta and pulmonary trunk. the opening of the superior vena cava, with fibers continuous An electrocardiogram (EKG) is used to record electri- with those of the atrial syncytium. cal changes in the myocardium during the cardiac cycle. The SA node’s cells can reach threshold on their own, ini- Although ECG is the correct abbreviation for electrocardio- tiating impulses through the myocardium, stimulating con- gram, the abbreviation EKG is more commonly used. Because traction of cardiac muscle© Jones fibers. Its & rhythmic Bartlett activity Learning, occurs LLCphlebotomists do not generally© perform Jones this & procedure, Bartlett it Learning,is LLC 70 to 80 times per minuteNOT in FORa normal SALE adult. ORSince DISTRIBUTIONit gener- not discussed in depth in this chapter.NOT FOR The most SALE important OR DISTRIBUTION ates the heart’s rhythmic contractions, it is often referred to ions that influence heart action are potassium and calcium. as the pacemaker. Excess extracellular potassium ions (hyperkalemia) decrease The path of a cardiac impulse travels from the SA node contraction rates and forces, while deficient extracellular into the atrial syncytium, and the atria begin to contract potassium ions (hypokalemia) may cause a potentially life- © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

R © Jones & Bartlett Learning, LLC Atrioventricular © Jones & Bartlett Learning, LLC bundle SINOATRIAL (SA) NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION NODE (pacemaker) Purkinje fibers

T Interventricular P © Jones & Bartlett Learning, LLC septum© Jones & Bartlett Learning, LLC ATRIOVENTRICULAR (AV)NOT NODE FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

QS Conduction myofibers Right and left (Purkinje fibers) branches of AV bundle © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEFigure 5–4 OR The DISTRIBUTION cardiac conduction system. Also shown is a tracingNOT of an FOREKG. The SALE P wave corresponds OR DISTRIBUTION to atrial depolarization, the QRS coplex to ventricular depolarization, and the T wave to ventricular repolarization. © Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION

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© Jones &threatening Bartlett Learning,abnormal heart LLC rhythm (arrhythmia). Excess© Jonesflow backward & Bartlett at this Learning, point due to LLC a valve malfunction, a extracellular calcium ions (hypercalcemia) can cause the heartNOT heart FOR murmur SALE will OR result. DISTRIBUTION To summarize, the right side of the NOT FOR SALEto contract OR for DISTRIBUTION an abnormally long time, while low extracel- heart pumps oxygen-poor blood to the lungs, and the left side lular calcium ions (hypocalcemia) depress heart action. pumps oxygen-rich blood toward the body tissues. The contraction of the heart is called systole, and its relax- systolic Functions of the Heart ation is called diastole. The blood pressure is the first © Jones & Bartlett Learning, LLCnumber in a blood pressure reading,© Jones measuring & Bartlett the strength Learning, LLC The heart chambers are coordinated so that their actions are of contraction. The diastolic blood pressure is the second effective. The atria contractNOT (atrialFOR systole SALE) as OR the ventriclesDISTRIBUTION number in a blood pressure reading,NOT measuring FOR SALE the strength OR DISTRIBUTION relax (ventricular diastole). Likewise, ventricles contract of relaxation. The right ventricle does not need to pump blood (ventricular systole) as atria relax (atrial diastole). Then a with as much force as the left ventricle. This is so because brief period of relaxation of both atria and ventricles occurs. the right ventricle supplies blood to the nearby lungs and the This complete series of events makes up a heartbeat, also pulmonary vessels are wide and relatively short. This means called© Jonesa cardiac &cycle. Bartlett Learning, LLC that the walls© of Jones the right &ventricle Bartlett are thinner Learning, and less LLCmus- OneNOT cardiac FOR cycle SALE causes OR pressure DISTRIBUTION in the heart chambers to cular than thoseNOT of the FOR left ventricle, SALE whichOR DISTRIBUTION must pump blood rise and fall and valves to open and close. Early during dias- to the entire body. tole, pressure in the ventricles is low, causing the AV valves to open and the ventricles to fill with blood. Nearly 70% of The Blood Vessels and Circulation returning blood enters the ventricles before contraction. As © Jones & theBartlett atria contract, Learning, the remaining LLC 30% is pushed into the ven©- JonesThe blood & Bartlett vessels of Learning,the human body LLC carry blood to every NOT FOR SALEtricles. As OR the DISTRIBUTIONventricles contract, ventricular pressure rises.NOT type FOR of tissue SALE and organ.OR DISTRIBUTION Vessels decrease in size as they move When ventricular pressure exceeds atrial pressure, the AV away from the heart (arteries and arterioles), ending in the valves close and papillary muscles contract, preventing the capillaries, and then increase in size as they move toward the cusps of the AV valves from bulging into the atria excessively. heart (venules and veins). The largest artery in the body is During ventricular contraction, the AV valves are closed, and the aorta, with the largest veins being the venae cavae, each atrial pressure is low.© Blood Jones flows & into Bartlett the atria Learning, while the LLCbeing approximately 1 in wide.© Jones & Bartlett Learning, LLC ventricles are contracting,NOT so FOR that the SALE atria are OR prepared DISTRIBUTION for Blood Vessels NOT FOR SALE OR DISTRIBUTION the next cardiac cycle. As ventricular pressure exceeds pulmonary trunk and There are five general classes of blood vessels in the cardio- aorta pressure, the pulmonary and aortic valves open. Blood is vascular system: arteries, arterioles, capillaries, venules, and ejected from the ventricles into these arteries, and ventricular veins (see Figure 5–5). Arteries are elastic vessels that are pressure© Jones drops. &When Bartlett ventricular Learning, pressure is LLC lower than in very strong,© able Jones to carry & blood Bartlett away from Learning, the heart underLLC the aorta and pulmonary trunk, the semilunar valves close. high pressure. They subdivide into thinner tubes that give WhenNOT ventricular FOR SALE pressure OR is lower DISTRIBUTION than atrial pressure, the rise to branched,NOT finer FOR arterioles SALE. AnOR artery’s DISTRIBUTION wall consists AV valves open, and the ventricles begin to refill. of three distinct layers, as shown in Figure 5–6. The inner- A heartbeat makes a characteristic double thumping most tunica interna is made up of a layer of simple squamous sound when heard through a stethoscope. This is due to the epithelium known as endothelium. It rests on a connective vibrations of the heart tissues related to the valves closing. tissue membrane with many elastic, collagenous fibers. The © Jones & TheBartlett first thumping Learning, sound LLC occurs during ventricular con©- Jonesendothelium & Bartlett helps prevent Learning, blood clotting LLC and may also help NOT FOR SALEtraction ORwhen DISTRIBUTION the AV valves close. The second sound occursNOT in FOR regulating SALE blood OR flow. DISTRIBUTION It releases nitric oxide to relax the during ventricular relaxation when the pulmonary and aor- smooth muscle of the vessel. Vein walls are similar but not tic valves close. identical to artery walls. Cardiac muscle fibers are similar in function to skeletal The middle tunica media makes up most of an arterial wall, muscle fibers, but are connected in branched networks. If any including smooth muscle fibers and a thick elastic connective part of the network is stimulated,© Jones impulses & Bartlett are sent Learning, through- LLCtissue layer. The outer tunica externa© Jones (tunica & adventitiaBartlett) isLearning, LLC functional out the heart, and it contractsNOT FOR as a single SALE unit. OR A DISTRIBUTIONthinner, mostly made up of connectiveNOT FOR tissue SALEwith irregular OR DISTRIBUTION syncytium is a mass of merging cells that functions as a unit. fibers—it is attached to the surrounding tissues. Smooth There are two of these structures in the heart: one in the atrial artery and arteriole muscles are innervated by the sympa- walls and another in the ventricular walls. A small area of the thetic nervous system. Vasomotor fibers receive impulses to right atrial floor is the only part of the heart’s muscle fibers contract and reduce blood vessel diameter (vasoconstriction). that© is Jones not separated & Bartlett by the heart’s Learning, fibrous skeleton.LLC Here, When inhibited,© Jones the muscle & fibersBartlett relax andLearning, the vessel’s diamLLC- cardiac conduction system fibers connect the atrial syncy- eter increases (vasodilation). Changes in artery and arteriole tiumNOT and theFOR ventricular SALE syncytium. OR DISTRIBUTION diameters greatlyNOT affect FOR blood SALE flow ORand pressure. DISTRIBUTION Newly oxygenated blood flows into the left and right pul- Larger arterioles also have three layers in their walls, which monary veins, returning to the left atrium (see Figure 5–3). get thinner as arterioles lead to capillaries. Very small arte- Blood then flows through the left atrioventricular (bicus- riole walls only have an endothelial lining and some smooth pid or mitral) valve into the left ventricle, passing through muscle fibers, with a small amount of surrounding connec- © Jones & theBartlett aortic semilunar Learning, valve LLCinto the systemic circuit (via the© Jonestive tissue. & Bartlett Learning, LLC NOT FOR SALEascending OR aorta DISTRIBUTION). The systemic circuit moves blood to theNOT FORThe smallest-diameter SALE OR DISTRIBUTION blood vessels are capillaries, which body tissues, supplying their required oxygen. Should blood connect the smallest arterioles to the smallest venules. The © Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION

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From heart To heart

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Elastic Muscular arteries Capillaries Venules and Large arteries NOT FORand arterioles SALE OR DISTRIBUTIONmedium veins veins NOT FOR SALE OR DISTRIBUTION

walls of capillaries are also composed of endothelium and cells. Capillary walls allow the diffusion of blood with high form the semipermeable layer through which substances levels of oxygen and nutrients. They also allow high levels of © Jones & inBartlett blood are Learning,exchanged with LLC substances in tissue fluids sur©- Jonescarbon & dioxide Bartlett and other Learning, wastes to move LLC from the tissues into NOT FOR SALErounding OR cells DISTRIBUTION of the body. NOTthe FOR capillaries. SALE Plasma OR proteinsDISTRIBUTION usually cannot move through Capillary walls have thin slits where endothelial cells over- the capillary walls due to their large size, so they remain in the lap. These slits have various sizes, affecting permeability. blood. Blood pressure generated when capillary walls contract Capillaries of muscles have smaller openings than those of provides force for filtration via hydrostatic pressure. the glands, kidneys, and small intestine. Tissues with higher metabolic rates (such as muscles) have many more capillaries © Jones & Bartlett Learning, LLC © Jones &� Bartlett Learning, LLC than those with slower metabolic rates (such as cartilage). NOT FOR SALE OR DISTRIBUTION Main StreetNOT FOR SALE OR DISTRIBUTION Some capillaries pass directly from arterioles to venules East Street while others have highly branched networks (see Figure 5–7). West Street 132 Precapillary sphincters control blood distribution through 65

capillaries. Based on the demands of cells, these sphincters 81 Clark Street constrict or relax so that blood can follow specific pathways © Jones & Bartlett Learning, LLC © Jones &Morales Bartlett Avenue Learning, LLC to meet tissue cellular requirements. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Gases, metabolic by-products, and nutrients are exchanged Bruno Street between capillaries and the tissue fluid surrounding body

Endothelium

Capillaries

Arteriole © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONTunica adventitia NOT FOR SALE OR DISTRIBUTION

Precapillary sphincters © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Figure 5–6 General structure of the blood vessel. The artery NOT FOR SALEshown here OR consists DISTRIBUTION of three major layers, the tunica intima, tunica NOTFigure FOR 5–7 SALE Similar OR to the DISTRIBUTION way roadways are designed, larger media, and tunica adventitia. arterioles and venules are interconnected with smaller capillaries. © Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION

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Blood Pressure © Jones & BartlettBlood pressure Learning, is strongest LLC when blood leaves the heart© Jones & Bartlett Learning, LLC NOT FOR SALEand weaker OR as theDISTRIBUTION distance from the heart increases because ofNOT Blood FOR pressure SALE is defined OR DISTRIBUTION as the force that blood exerts against friction (peripheral resistance) between the blood and the ves- the inner walls of blood vessels. It most commonly refers to sel walls. Therefore, blood pressure is highest in the arteries, pressure in arteries supplied by the aortic branches, even less so in the arterioles, and lowest in the capillaries. Filtration though it actually occurs throughout the vascular system. occurs mostly at the arteriolar ends of capillaries because the Arterial blood pressure rises and falls according to cardiac pressure is higher than© at Jones the venular & Bartlettends. Plasma Learning, proteins LLCcycle phases. The maximum ©pressure Jones during & Bartlett ventricular Learning, LLC trapped in capillaries create an osmotic pressure that pulls systolic pressure NOT FOR SALE OR DISTRIBUTIONcontraction is called the NOT FOR. SALE OR DISTRIBUTION water into the capillaries (colloid osmotic pressure). The lowest pressure that remains in the arteries before Capillary blood pressure favors filtration while plasma the next ventricular contraction is called the diastolic pres- colloid osmotic pressure favors reabsorption. At the venu- sure. Arterial blood pressure is measured with a device called lar ends of capillaries, blood pressure has decreased due to a sphygmomanometer (blood pressure cuff). Its results are resistance so that reabsorption can occur. © Jones & Bartlett Learning, LLC reported as ©a fraction Jones of &the Bartlett systolic pressure Learning, over the LLC dia- More fluid usually leaves capillaries than returns to them. stolic pressure, such as 120/80. The upper (first) number LymphaticNOT FORcapillaries SALE have closed OR DISTRIBUTIONends and collect excess fluid indicates theNOT arterial FOR systolic SALE pressure OR in millimeters DISTRIBUTION of mer- to return it via lymphatic vessels to the venous circulation. cury (mm Hg), and the lower (second) number indicates the Unusual events may cause excess fluid to enter spaces between arterial diastolic pressure, also in millimeters of mercury. A tissue cells, often in response to chemicals such as histamine. If millimeter of mercury is a unit of pressure that is equal to enough fluid leaks out, lymphatic vessels can be overwhelmed, 0.001316 of normal atmospheric pressure. This means that a © Jones & andBartlett affected Learning,tissues swell and LLC become painful. © Jonesblood pressure& Bartlett of 120/80 Learning, displaces 120 LLC mm Hg on a sphygmo- Venules NOT FOR SALE OR are DISTRIBUTION microscopic vessels that link capillaries toNOT manometer, FOR SALE showing OR the DISTRIBUTION systolic pressure, and also displaces veins , which carry blood back to the atria. Vein walls are 80 mm Hg on the same device, showing diastolic pressure. similar to arteries but have poorly developed middle layers. Figure 5–8 shows changes in blood pressure as the distance Because they have thinner walls that are less elastic than from the left ventricle increases. arteries, their lumens have a greater diameter. The artery walls are distended as blood surges into them Many veins have flaplike© Jones valves & projecting Bartlett inward Learning, from LLCfrom the ventricles, but they recoil© Jones almost immediately. & Bartlett This Learning, LLC their linings. These valvesNOT often FOR have twoSALE structures OR thatDISTRIBUTION close expansion and recoiling can be feltNOT as a FORpulse in SALE an artery OR near DISTRIBUTION if blood begins to back up in the vein. They aid in returning the surface of the skin. Most commonly, the radial artery is blood to the heart, opening if blood flow is toward the heart, used to take a person’s pulse, although the carotid, brachial, but closing if it reverses. Unlike the arteries, veins do not and femoral arteries are also checked. Arterial blood pres- have sufficient pressure from the contractions of the heart sure depends on heart rate, stroke volume, blood volume, to keep© Jones blood moving & Bartlett through Learning,them. To keep LLCblood flowing, peripheral resistance,© Jones and & blood Bartlett viscosity. Learning, LLC the veins rely on the movement of nearby skeletal muscles, NOT FOR SALE OR DISTRIBUTION Heart actionNOT determines FOR SALE the amount OR DISTRIBUTIONof blood entering as well as the opening and closing of the valves within them. the arterial system with each ventricular contraction. Stroke Therefore, a major structural difference between veins and volume is defined as the volume of blood discharged from arteries is that arteries do not have valves. the ventricle with each contraction. An average adult male’s Veins also act as reservoirs for blood in certain conditions, stroke volume is about 70 mL. The cardiac output is defined such as during arterial hemorrhage. Resulting venous con- as the volume discharged from the ventricle per minute. It is © Jones & strictionsBartlett help Learning, to maintain bloodLLC pressure by returning more© Jonescalculated & Bartlett by multiplying Learning, the stroke volumeLLC by the heart rate, NOT FOR SALEblood to OR the heart,DISTRIBUTION ensuring an almost normal blood flowNOT in FOR beats perSALE minute. OR So DISTRIBUTIONif the stroke volume is 70 mL and the even when up to one-quarter of the blood volume is lost. See heart rate is 75 beats per minute (bpm), the cardiac output Table 5–2 for a summary of blood vessel characteristics. is 5,250 mL/min. Blood pressure varies with cardiac output

■■Table 5–2 Characteristics© Jones of Blood & Bartlett Vessels Learning, LLC © Jones & Bartlett Learning, LLC Type of Vessel VesselNOT Wall FOR SALE OR DISTRIBUTIONActions NOT FOR SALE OR DISTRIBUTION Artery Three-layer thick wall (endothelial lining, middle smooth Carries relatively high-pressure blood from the heart to the muscle and elastic connective tissue layer, and outer arterioles connective tissue layer) Arteriole Three-layer thinner wall (smaller arterioles have an Helps control blood flow from arteries to capillaries by © Jones & Bartlettendothelial Learning, lining, some smooth LLC muscle tissue, and a vasoconstriction© Jones & or Bartlettvasodilation Learning, LLC NOT FOR SALEsmall ORamount DISTRIBUTION of connective tissue) NOT FOR SALE OR DISTRIBUTION Capillary One layer of squamous epithelium Has a membrane allowing nutrients, gases, and wastes to be exchanged between blood and tissue fluid Venule Thinner wall than arterioles, with less smooth muscle and Connects capillaries to veins elastic connective tissue © Jones & BartlettVein Learning,Thinner wall LLC than arteries but similar layers; poorly© Jones &Carries Bartlett relatively Learning, low-pressure blood LLC from venules to the NOT FOR SALE OR DISTRIBUTIONdeveloped middle layer; some have flaplikeNOT valves FOR SALEheart; valves OR preventDISTRIBUTION blood backflow; veins serve as blood reservoirs

99069_ch05_6101.indd 43 2/3/12 2:09:05 PM 44 CHAPTER 5 Anatomy and Physiology of the Cardiovascular System

© Jones &and Bartlett increases Learning, or decreases LLC based upon similar changes in© Jones & Bartlett Learning, LLC stroke volume or heart rate. NOT FOR SALE OR DISTRIBUTION NOT FOR SALEBlood OR volume DISTRIBUTION is defined as the sum of formed elements and plasma volumes in the vascular system. Blood volume varies with age, body size, and gender. Most adults have approximately 5 L of blood, which makes up 8% of the body weight in kilograms. Blood© Jones pressure & andBartlett volume Learning,are usually LLC © Jones & Bartlett Learning, LLC directly proportional. Any changes in volume can initially alter pressure. When NOTmeasures FOR are takenSALE to restoreOR DISTRIBUTION normal NOT FOR SALE OR DISTRIBUTION blood volume, normal blood pressure can be reestablished. Fluid balance fluctuations may also affect blood volume. The resistance of arteries to blood flow is defined as Direction of blood flow peripheral resistance. The degree of peripheral resistance is determined© Jones by & theBartlett blood vessel Learning, diameter LLCand the force © Jones & BartlettTotal Learning, cross-sectional LLC area of vessels of contractionNOT FOR exerted SALE by vascularOR DISTRIBUTION smooth muscle. There- NOT FOR SALE OR DISTRIBUTION fore, peripheral resistance is a factor that accounts for blood Blood pressure. pressure Viscosity is defined as the resistance of a fluid to flow. In a biologic fluid, viscosity is caused by the attraction of mol- © Jones & eculesBartlett or cells Learning, to one another. LLC The higher the viscosity, the© Jones & Bartlett Learning, LLC NOT FOR SALEgreater the OR resistance DISTRIBUTION to flowing. Blood viscosity is increasedNOT FOR SALE OR DISTRIBUTION by blood cells and plasma proteins. The greater the resistance, Velocity of blood the greater the force needed to move the blood. Blood pressure rises as blood viscosity increases, and vice versa. Blood pressure (BP) is calculated by multiplying cardiac output (CO) by peripheral© Jones resistance & Bartlett (PR). Normal Learning, arterial LLC © Jones & Bartlett Learning, LLC pressure is maintainedNOT by regulating FOR SALE these two OR factors. DISTRIBUTION Ide- NOT FOR SALE OR DISTRIBUTION ally, the volume of blood discharged from the heart should be equal to the volume entering the atria and ventricles. Fiber length and force of contraction are interrelated because of the stretching of the cardiac muscle cell just before contraction. Arteries Capillaries Veins This© is Jones known as& the Bartlett Frank-Starling Learning, law of the LLC heart, and it © JonesArterioles & BartlettVenules Learning, LLC is important during exercise when greater amounts of blood returnNOT to theFOR heart SALE from the OR veins. DISTRIBUTION Figure 5–8 NOTBlood pressure FOR inSALE the circulatory OR system.DISTRIBUTION Blood Peripheral resistance also controls blood pressure. pressure declines in the circulatory system as the vessels branch. Arterial pressure pulses because of the heartbeat, but pulsation is Changes in the diameters of arterioles regulate peripheral lost by the time the blood reaches the capillary networks, creating an resistance. The vasomotor center of the medulla oblongata even flow through body tissues. Blood pressure continues to decline controls peripheral resistance. When arterial blood pressure in the venous side of the circulatory system. © Jones & increasesBartlett suddenly, Learning, baroreceptors LLC in the aorta and carotid© Jones & Bartlett Learning, LLC NOT FOR SALEarteries ORalert DISTRIBUTIONthe vasomotor center, which vasodilates theNOT FOR SALE OR DISTRIBUTION vessels to decrease peripheral resistance. Carbon dioxide, arteries, which enter the right and left lungs, respectively. oxygen, and hydrogen ions also influence peripheral resis- Repeated divisions connect to arterioles and capillary net- tance by affecting precapillary sphincters and smooth arte- works associated with the walls of the alveoli, where gas is riole wall muscles. exchanged between blood and air. The pulmonary capillaries Blood flow through© Jones the venous & systemBartlett depends Learning, only LLClead to venules and then veins.© Four Jones pulmonary & Bartlett veins, two Learning, LLC slightly on heart action,NOT but more FOR so SALEon skeletal OR muscle DISTRIBUTION con- from each lung, return blood toNOT the left FOR atrium, SALE completing OR DISTRIBUTION traction, movements of breathing, and the vasoconstriction the vascular loop of the pulmonary circuit. of veins (venoconstriction). As skeletal muscles press on veins The systemic circuit involves the movement of freshly with valves, some blood moves from one valve section to oxygenated blood from the left atrium to left ventricle, then another, helping to push blood forward through the venous into the aorta and its branches, leading to all body tissues. system© Jones to the heart. & Bartlett During inspiration, Learning, thoracic LLC cavity pres- Eventually it© makes Jones its way& Bartlett to the companion Learning, vein system LLC that returns blood to the right atrium. sureNOT is reduced FOR while SALE abdominal OR DISTRIBUTIONcavity pressure is increased. NOT FOR SALE OR DISTRIBUTION Blood is then squeezed out of abdominal veins and forced into The Arteries thoracic veins. When venous pressure is low, the walls of the veins contract to help force blood out toward the heart. The largest-diameter artery in the body is the aorta, extend- Blood Circulation ing upward from the left ventricle to arch over the heart to the left, descending anterior and to the left of the vertebral © Jones & BloodBartlett enters Learning, the pulmonary LLC circuit from the right ventricle© Jonescolumn. & The Bartlett first portion Learning, of the aorta LLC is called the ascending NOT FOR SALEthrough ORthe pulmonary DISTRIBUTION trunk, which extends upward posteNOT- aorta FOR. It SALEbegins at OR the aorticDISTRIBUTION valve of the left ventricle. The riorly from the heart. It divides into right and left pulmonary left and right coronary arteries originate in the aortic sinus. © Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION

99069_ch05_6101.indd 44 2/3/12 2:09:06 PM The Blood Vessels and Circulation 45

© Jones &This Bartlett origination Learning, occurs at LLCthe base of the ascending aorta,© JonesThe & posterior Bartlett cerebral Learning, arteries helpLLC form the cerebral arterial circle slightly superior to the aortic valve. NOT FOR SALE (also OR known DISTRIBUTION as the circle of Willis), connecting NOT FOR SALEThe aortic OR DISTRIBUTIONarch curves across the superior surface of the the vertebral artery and internal carotid artery systems (see heart. It connects the ascending aorta with the descending Figure 5–10). These united systems provide alternate blood aorta (see Figure 5–9). Three arteries originate along the pathways to circumvent blockages and reach brain tissues and aortic arch. They deliver blood to the head, neck, shoulders, to equalize blood pressure in the brain’s blood supply. thyrocervical arteries and upper limbs. These© arteriesJones are & as Bartlett follows: Learning, LLCThe give© Jones off branches & Bartlettto the thyroid Learning, LLC 1. The brachiocephalic trunk and parathyroid glands, larynx, trachea, esophagus, pharynx, 2. The left commonNOT carotid FOR artery SALE OR DISTRIBUTIONand muscles of the neck, shoulder,NOT and FOR back. SALE The left OR and DISTRIBUTION 3. The left subclavian artery right common carotid arteries separate into the internal and The brachiocephalic trunk ascends only for a short distance external carotid arteries. Table 5–4 discusses these arter- before it branches to form the right subclavian and right com- ies. Near the base of the carotid arteries are enlargements mon carotid arteries. The descending aorta is continuous (carotid sinuses) that contain baroreceptors and help to with© the Jones aortic arch.& Bartlett The diaphragm Learning, divides theLLC descending control blood© pressure. Jones & Bartlett Learning, LLC aortaNOT into aFOR superior SALE thoracic OR aorta DISTRIBUTION and an inferior abdomi- The subclavianNOT artery,FOR whichSALE is aOR branch DISTRIBUTION of the brachio- nal aorta. The branches of the thoracic aorta include the cephalic artery, continues into the arm, passing between the bronchial, pericardial, esophageal, mediastinal, and inter- clavicle and first rib to become the axillary artery. It becomes costal arteries. the brachial artery and gives rise to a deep brachial artery. The abdominal aorta, beginning immediately inferior to The ulnar artery leads down to the lower arm, on the ulnar © Jones & theBartlett diaphragm, Learning, is a continuation LLC of the thoracic aorta (see© Jonesside of &the Bartlett forearm to Learning, the wrist. Some LLC of its branches supply NOT FOR SALEFigure 5–9). OR It DISTRIBUTION delivers blood to the abdominopelvic organsNOT the FOR elbow SALE joint, while OR othersDISTRIBUTION supply the muscles of the fore- and structures. The abdominopelvic branches of the aorta arm. The radial artery provides blood to the wrist and hand, include the following: celiac, phrenic, superior mesenteric, traveling along the radial side of the forearm to the wrist. It suprarenal, renal, gonadal, inferior mesenteric, lumbar, mid- also supplies the lateral muscles of the forearm. Near the dle sacral, and common lilac arteries. Table 5–3 summarizes wrist, it approaches the surface, providing a point where the the major branches of© the Jones aorta. & Bartlett Learning, LLCradial pulse may easily be taken.© Jones & Bartlett Learning, LLC The subclavian andNOT common FOR carotid SALE arteries OR supply DISTRIBUTION blood The internal thoracic arteryNOT branches FOR into SALE two anterior OR DISTRIBUTION to the neck, head, and brain. The main divisions of these intercostal arteries supplying the intercostal muscles and arteries are the vertebral and thyrocervical arteries. The mammary glands. The posterior intercostal arteries supply vertebral arteries run upward through the cervical verte- other intercostal muscles as well as the vertebrae, spinal cord, brae into the skull and supply blood to the vertebrae and to and deeper back muscles. The internal thoracic artery and their© ligamentsJones &and Bartlett muscles. TheyLearning, unite in the LLC cranial cav- external iliac© artery Jones provide & Bartlett blood to the Learning, anterior abdomi LLC- ity to form the basilar artery, which branches to the pons, nal wall while the phrenic artery and lumbar artery supply midbrain,NOT FORand cerebellum. SALE ORIt ultimately DISTRIBUTION divides into the two blood to posteriorNOT and FOR lateral SALE abdominal OR wall DISTRIBUTION structures. The posterior cerebral arteries. major vessels of the arterial system include the common iliac

© Jones & ■Bartlett■Table 5–3 Learning, Major Branches LLC of the Aorta © Jones & Bartlett Learning, LLC NOT FOR SALEBranch OR DISTRIBUTION Area of AortaNOT FOR SALEMain OR Regions DISTRIBUTION or Organs Supplied Right and left coronary arteries Ascending aorta Heart Brachiocephalic artery Arch of the aorta Right upper limb and right side of head Left common carotid artery Left side of head Left subclavian artery Left upper limb Descending aorta: © Jones & Bartlett Learning,Thoracic aorta LLC © Jones & Bartlett Learning, LLC Bronchial artery NOT FOR SALE OR DISTRIBUTION Bronchi NOT FOR SALE OR DISTRIBUTION Pericardial artery Pericardium Esophageal artery Esophagus Mediastinal artery Mediastinum Posterior intercostal artery Thoracic wall Descending aorta: Abdominal aorta Celiac© Jones artery & Bartlett Learning, LLC © UpperJones digestive & Bartlett tract organs Learning, LLC PhrenicNOT artery FOR SALE OR DISTRIBUTION NOTDiaphragm FOR SALE OR DISTRIBUTION Superior mesenteric artery Small and large intestines Suprarenal artery Adrenal gland Renal artery Kidney Gonadal artery Ovaries or testes Inferior mesenteric artery Lower large intestine © Jones & BartlettLumbar artery Learning, LLC © Jones & BartlettAbdominal Learning, wall (posterior) LLC NOT FOR SALEMiddle sacral OR artery DISTRIBUTION NOT FOR SALESacrum OR and DISTRIBUTION coccyx Common iliac artery Lower abdominal wall, pelvic organs, lower limbs

99069_ch05_6101.indd 45 2/3/12 2:09:06 PM 46 CHAPTER 5 Anatomy and Physiology of the Cardiovascular System

Internal carotid artery External carotid© Jones artery & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Vertebral artery Common carotid arteries NOT FOR SALE OR DISTRIBUTION SubclavianNOT FOR artery SALE OR DISTRIBUTION Brachiocephalic trunk Axillary artery Arch of the aorta

Ascending aorta Descending aorta © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Brachial artery Thoracic aorta Branches of celiac trunk Abdominal aorta Superior mesenteric artery Renal artery © Jones & BartlettInferior mesentericLearning, artery LLC © Jones & Bartlett Learning,Gonadal LLC artery NOT FOR SALECommon OR iliacDISTRIBUTION artery NOT FOR SALE OR DISTRIBUTIONRadial artery External iliac artery Ulnar artery

Deep palmar artery

Superficial palmar artery© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Digital arteries NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Femoral artery

Anterior tibial artery © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Posterior tibial artery Peroneal artery © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Arcuate artery

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Middle cerebral artery © Jones & Bartlett Learning, LLC © Jones & BartlettCommon iliacLearning, artery LLC Internal iliac artery NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Posterior cerebral External iliac artery artery Internal pudental artery Anterior cerebral artery Obturator artery Circle of Willis Ophthalmic Superficial © Jones & Bartlett Learning, LLC Deep femoral artery © Jones & Bartlett Learning, LLC artery temporal artery NOT FOR SALE OR DISTRIBUTION Lateral femoral NOT FOR SALE OR DISTRIBUTION Basilar artery Maxillary circumflex artery artery Vertebral artery Medial femoral Facial circumflex artery artery Internal carotid artery External© Jones carotid artery & Bartlett Learning, LLC ©Femoral Jones artery & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Lingual artery NOT FOR SALE OR DISTRIBUTION Common carotid artery Superior thyroid artery

Thyrocervical artery Popliteal artery

© Jones & SubclavianBartlett artery Learning, LLC Brachiocephalic© Jones trunk & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Arch of the aorta Anterior tibial artery

(a) Ascending aorta Descending aorta

Common carotid© arteryJones & Bartlett Learning, LLC Posterior tibial artery © Jones & Bartlett Learning, LLC Vertebral arteryNOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Peroneal artery Thyrocervical artery

Costocervical artery Suprascapula artery Thoracoacromial© Jones artery & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC AxillaryNOT artery FOR SALE OR DISTRIBUTION NOTDorsalis FOR pedis artery SALE OR DISTRIBUTION Posterior humeral Arcuate artery Medial circumflex artery plantar Anterior humeral artery circumflex artery Metatarsal arteries Brachial artery (c) © Jones & DeepBartlett brachial arteryLearning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Radial artery Ulnar artery © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Deep palmar artery © Jones & Bartlett Learning,Superficial palmar LLC artery © Jones & Bartlett Learning, LLC NOT FOR SALE ORDigital DISTRIBUTION arteries NOT FOR SALE OR DISTRIBUTION (b)

Figure 5–10 Detailed views of the arteries in the body © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

99069_ch05_6101.indd 47 2/3/12 2:09:11 PM 48 CHAPTER 5 Anatomy and Physiology of the Cardiovascular System

■■Table 5–4 Major Branches of the Carotid Arteries © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Branch Carotid Artery Main Regions or Organs Supplied NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Superior thyroid artery External Larynx and thyroid gland Lingual artery Salivary glands and tongue Facial artery Chin, lips, nose, palate, and pharynx Occipital artery Meninges, neck muscles, and posterior scalp Posterior auricular artery Ear and lateral scalp Maxillary artery © Jones & Bartlett Learning, LLC Cheeks, eyelids, jaw, and© teethJones & Bartlett Learning, LLC Superficial temporal arteryNOT FOR SALE OR DISTRIBUTION Parotid salivary gland andNOT surface FOR of face SALE and scalp OR DISTRIBUTION Ophthalmic artery Internal Eyes and eye muscles Anterior choroid artery Brain and choroid plexus Anterior cerebral artery Frontal and parietal lobes of brain

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC arteriesNOT, internal FOR iliac SALE artery OR, femoral DISTRIBUTION artery, popliteal artery, Veins thatNOT drain bloodFOR from SALE the lower OR limbs DISTRIBUTION are also subdi- anterior tibial artery, and posterior tibial artery. vided, like those of the upper limbs, into deep and superficial groups. The deep anterior tibial vein and posterior tibial vein The Veins merge to from the popliteal vein (which is located deep in The vessels of the venous system are more difficult to follow the leg, behind the knee), continuing upward as the femoral © Jones & thanBartlett those of Learning, the arterial system. LLC They connect in irregular© Jonesvein and & thenBartlett the external Learning, iliac vein .LLC NOT FOR SALEnetworks, OR with DISTRIBUTION many unnamed vessels joining to form largerNOT FORThe saphenousSALE OR veins DISTRIBUTION of the lower leg communicate with veins. Larger veins typically parallel the locations of arteries one another as well as the deeper veins of the leg and thigh, and have similar names. The veins from all parts of the body allowing blood to return to the heart from the lower extremi- besides the lungs and heart converge into the superior vena ties by several routes. In the pelvis, vessels carry blood away cava and inferior vena cava, leading to the right atrium. from the reproductive, urinary, and digestive organs via the The external jugular© Jonesveins descend & Bartlett on either Learning,side of the LLCinternal iliac veins. These unite© with Jones the external & Bartlett iliac veins Learning, LLC neck and empty into NOTthe right FOR subclavian SALE vein OR and DISTRIBUTION left sub- to form the common iliac veinsNOT and eventuallyFOR SALE the inferior OR DISTRIBUTION clavian vein (see Figure 5–11). The internal jugular veins vena cava. The great saphenous vein runs the entire length descend through the neck to join the subclavian veins, form- of the leg (see Figure 5–12c) and is considered the longest ing brachiocephalic veins on each side, above the clavicles. vein in the body. They then merge to form the superior vena cava. ©Deep Jones and superficial & Bartlett veins Learning, drain the upper LLC limbs and Summary© Jones & Bartlett Learning, LLC shoulders. The superficial veins connect via complex net- worksNOT just FORunder theSALE skin and OR communicate DISTRIBUTION with the deeper The cardiovascularNOT FOR system SALE consists OR of the DISTRIBUTION heart and blood vessels (see Figure 5–12). The basilic vein ascends to join the vessels. It provides oxygen and nutrients to tissues while brachial vein, merging to form the axillary vein. The cephalic removing wastes. The heart is located within the mediasti- vein ascends upward to empty into the axillary vein, and later num, resting on the diaphragm. The wall of the heart has it becomes the subclavian vein. three layers: the epicardium, myocardium, and endocardium. © Jones & BartlettThe brachiocephalic Learning, and LLC azygos veins drain the abdomi©- JonesThe heart & Bartlett is divided intoLearning, two atria and LLC two ventricles. Blood NOT FOR SALEnal and thoracicOR DISTRIBUTION walls. The azygos vein ascends through theNOT low FOR in oxygen SALE and OR high inDISTRIBUTION carbon dioxide enters the right side mediastinum to join the superior vena cava. Its tributaries of the heart and is pumped into the pulmonary circulation. include the posterior intercostal veins, superior hemiazy- After oxygenation in the lungs and some removal of carbon gos veins, and inferior hemiazygos veins. The right and left dioxide, it returns to the left side of the heart. The left ven- ascending lumbar veins have vessels from the lumbar and tricle pumps blood out of the heart to the rest of the body. sacral regions. © Jones & Bartlett Learning, LLCThe cardiac cycle consists of© the Jones atria contracting & Bartlett while Learning, LLC Most veins carry bloodNOT directly FOR to SALE the heart’s OR atria, DISTRIBUTION except the ventricles relax, and vice versa.NOT Electrical FOR SALEactivity ofOR the DISTRIBUTION for veins that drain the abdominal viscera (see Figure 5–13). cardiac cycle can be recorded via an electrocardiogram. The They originate in the stomach, intestines, pancreas, and cardiac cycle consists of the P wave, QRS complex, and T spleen to carry blood through a hepatic portal vein to the wave. Blood vessels form a closed circuit of tubes that carry liver. This pathway is called the hepatic portal system. It blood from the heart to the body cells and back again. This includes© Jones the right & andBartlett left gastric Learning, veins, superior LLC mesenteric circuit consists© Jonesof arteries, & arterioles, Bartlett capillaries, Learning, venules, LLC and veinNOT, and splenicFOR veinSALE. OR DISTRIBUTION veins. BloodNOT pressure FOR is the SALE force that OR blood DISTRIBUTION exerts against The liver helps to regulate blood concentrations of the insides of blood vessels. It is measured as systolic pres- absorbed amino acids and lipids. It modifies them into usable sure over diastolic pressure, meaning the pressure produced cells, oxidizes them, or changes them into forms that can be during ventricular contraction over the pressure produced stored. Hepatic portal venous blood usually contains bacte- when the ventricles relax. © Jones & riaBartlett from intestinal Learning, capillaries. LLC Large Kupffer cells in the liver© JonesThe & pulmonary Bartlett circuit Learning, consists of LLC vessels that carry blood phagocytize microorganisms before they can leave the liver. from the right ventricle to the lungs and back to the left NOT FOR SALEThis blood OR then DISTRIBUTION travels through merged vessels into hepaticNOT atrium. FOR TheSALE systemic OR DISTRIBUTIONcircuit consists of vessels that lead veins, emptying into the inferior vena cava. from the left ventricle to the body cells and back to the heart, © Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION

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External jugular vein Vertebral vein© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Internal jugularNOT vein FOR SALE OR DISTRIBUTION Subclavian veinNOT FOR SALE OR DISTRIBUTION

Superior vena cava Brachiocephalic veins Axillary vein

© Jones & Bartlett Learning, LLC © JonesCephalic & Bartlett vein Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FORBrachial SALE vein OR DISTRIBUTION Basilic vein Hepatic portal vein Splenic vein Superior mesenteric vein Renal vein Inferior vena cava Inferior mesenteric vein © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE ORCommon DISTRIBUTION iliac vein NOT FOR SALE OR DISTRIBUTIONRadial vein Internal iliac vein Ulnar vein

External iliac vein

Digital veins NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Femoral vein Great saphenous vein © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Popliteal vein NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Posterior tibial vein © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONAnterior tibial vein NOT FOR SALE OR DISTRIBUTION Small saphenous vein

Dorsal digital veins

© Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Figure 5–11 Overview of the veins in the body. For clarity, the right kidney is not shown. NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

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Straight sinus Facial vein Internal iliac vein External iliac vein © Jones & Bartlett Learning,Ophthalmic LLC vein © Jones & Bartlett Learning, LLC Superficial Occipital vein Femoral NOT FOR SALE OR DISTRIBUTIONtemporal vein circumflex vein NOT FOR SALE OR DISTRIBUTION Transverse sinus Posterior auricular vein Deep femoral vein

External jugular vein Femoral vein Vertebral vein © Jones & Bartlett Learning, LLC © GreatJones saphenous & Bartlett vein Learning, LLC InternalNOT jugular FOR vein SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Superior and middle thyroid veins

Right brachiocephalic vein

Subclavian vein Popliteal vein © Jones & Bartlett Learning, LLC Left brachiocephalic© Jones vein & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION Superior vena cava

(a) Small saphenous vein © Jones & Bartlett Learning, LLC Posterior tibial vein© Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION Anterior tibial veinNOT FOR SALE OR DISTRIBUTION Subclavian vein Brachiocephalic vein

Axillary© Jones vein & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC Superior NOT FOR SALE OR DISTRIBUTION vena cava NOTDorsal FOR venous SALE arch OR DISTRIBUTION Brachial vein Cephalic vein Metatarsal veins Basilic vein (c)

Median antebrachial © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC vein Basilic vein NOT FORUlnar vein SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

Deep palmar venous arch © Jones & BartlettSuperficial palmarLearning, LLC © Jones & Bartlett Learning, LLC venous arch NOT FOR SALEDigital veins OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

(b)

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© Jones &including Bartlett the Learning, aorta and its branches.LLC The aorta is the largest© Jones6. The& Bartlett function of Learning, an atrium is toLLC artery in the body, with respect to diameter. NOT FORA. SALE pump blood OR toDISTRIBUTION the lungs NOT FOR SALE OR DISTRIBUTION B. pump blood into the systemic circuit CRITICAL THINKING C. pump blood to the heart muscle D. collect blood Two phlebotomists were studying together to take the 7. The left and right pulmonary arteries carry blood to National Certification Exam. One of them was question- the ing the other about the© anatomy Jones and & physiologyBartlett ofLearning, the heart LLC © Jones & Bartlett Learning, LLC A. brain and circulatory system. The questions that follow were what NOT FOR SALE OR DISTRIBUTIONB. liver NOT FOR SALE OR DISTRIBUTION he asked. C. lungs 1. How many veins return blood to the right atrium? D. kidneys Name these veins. 8. The pacemaker cells of the heart are located in the 2. Where in the heart are the Purkinje fibers located? A. SA node 3. Where is the lowest blood pressure found in the blood © Jones & Bartlett Learning, LLC B. AV© node Jones & Bartlett Learning, LLC vessels? NOT FOR SALE OR DISTRIBUTION C. leftNOT ventricle FOR SALE OR DISTRIBUTION WEBSITES D. left atrium 9. Which of the following blood vessels returns blood to http://lsa.colorado.edu/essence/texts/heart.html the left atrium? A. inferior vena cava http://www.americanheart.org/presenter. © Jones & Bartlett Learning, LLC © Jones B.& Bartlettsuperior vena Learning, cava LLC jhtml?identifier=4473 NOT FOR SALE OR DISTRIBUTION NOT FORC. SALEpulmonary OR vein DISTRIBUTION http://www.ivy-rose.co.uk/HumanBody/Blood/Heart D. pulmonary trunk _Structure.php 10. Each of the following factors will increase cardiac out- http://www.nhlbi.nih.gov/health/dci/Diseases/hhw/hhw put, EXCEPT _circulation.html A. increased parasympathetic stimulation http://www.texasheart.org/hic/anatomy/© Jones & Bartlett Learning, LLC B. increased sympathetic© stimulationJones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTIONC. increased venous returnNOT FOR SALE OR DISTRIBUTION http://www.thic.com/conduction.htm D. increased heart rate http://www.tpub.com/content/medical/14295/css/14295_36 11. The difference between the systolic and diastolic pres- .htm sures is referred to as A. a pulse REVIEW QUESTIONS © Jones & Bartlett Learning, LLC B. circulatory© Jones pressure & Bartlett Learning, LLC C. blood pressure MultipleNOT ChoiceFOR SALE OR DISTRIBUTION D. meanNOT arterial FOR pressure SALE OR DISTRIBUTION 12. Blood from the brain returns to the heart via a vein 1. Blood leaving the left ventricle enters the called the A. pulmonary trunk A. external jugular B. pulmonary artery B. internal jugular C. inferior vena cava © Jones & Bartlett Learning, LLC © Jones C.& Bartlettvertebral vein Learning, LLC D. aorta D. azygos vein NOT FOR SALE2. The OR right DISTRIBUTION ventricle pumps blood to the NOT FOR SALE OR DISTRIBUTION 13. Branches off of the aortic arch include the A. systemic circuit A. brachio and right axillary arteries B. lungs B. right and left subclavian arteries C. left atrium C. right and left common carotid arteries D. right atrium © Jones & Bartlett Learning, LLC D. left subclavian and left© commonJones carotid& Bartlett arteries Learning, LLC 3. The visceral pericardium is the same as the 14. Nutrients from the digestive tract enter the A. epicardiumNOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION A. hepatic vein B. endocardium B. hepatic portal vein C. myocardium C. inferior vena cava D. parietal pericardium D. azygos vein 4. The mitral valve is located between the 15. The longest vein in the human body is the © JonesA. right atrium& Bartlett and right Learning, ventricle LLC © Jones & Bartlett Learning, LLC A. inferior vena cava B. left atrium and left ventricle NOT FOR SALE OR DISTRIBUTION B. superiorNOT venaFOR cava SALE OR DISTRIBUTION C. left ventricle and aorta C. saphenous vein D. right ventricle and pulmonary trunk D. femoral vein 5. The heart wall is composed of how many layers? A. two © Jones & BartlettB. three Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALEC. ORfour DISTRIBUTION NOT FOR SALE OR DISTRIBUTION D. five © Jones and Bartlett Publishers. NOT FOR SALE OR DISTRIBUTION

99069_ch05_6101.indd 51 2/3/12 2:09:16 PM © Jones & Bartlett Learning, LLC © Jones & Bartlett Learning, LLC NOT FOR SALE OR DISTRIBUTION NOT FOR SALE OR DISTRIBUTION

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