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The Heart

The Heart. Chapter 20. An Introduction to the Cardiovascular System. Learning Outcomes 20-1 Describe the anatomy of the heart, including vascular supply and pericardium structure, and trace the flow of blood through the heart, identifying the major blood vessels, chambers, and heart valves.

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The Heart

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  1. The Heart Chapter 20

  2. An Introduction to the Cardiovascular System • Learning Outcomes • 20-1 Describe the anatomy of the heart, including vascular supply and pericardium structure, and trace the flow of blood through the heart, identifying the major blood vessels, chambers, and heart valves. • 20-2 Explain the events of an action potential in cardiac muscle, indicate the importance of calcium ions to the contractile process, describe the conducting system of the heart, and identify the electrical events associated with a normal electrocardiogram.

  3. An Introduction to the Cardiovascular System • Learning Outcomes • 20-3 Explain the events of the cardiac cycle, including atrial and ventricular systole and diastole, and relate the heart sounds to specific events in the cycle. • 20-4 Define cardiac output, describe the factors that influence heart rate and stroke volume, and explain how adjustments in stroke volume and cardiac output are coordinated at different levels of physical activity.

  4. An Introduction to the Cardiovascular System • The PulmonaryCircuit • Carries blood to and from gas exchange surfaces of lungs • The SystemicCircuit • Carries blood to and from the body • Blood alternates between pulmonary circuit and systemic circuit

  5. An Introduction to the Cardiovascular System • Three Types of Blood Vessels • Arteries • Carry blood away from heart • Veins • Carry blood to heart • Capillaries • Networks between arteries and veins • Also called exchangevessels • Exchange materials between blood and tissues • Materials include dissolved gases, nutrients, waste products

  6. Pulmonary Circuit Systemic Circuit Systemic arteries Pulmonary arteries Systemic veins Pulmonary veins Capillariesin head,neck, upper limbs Capillariesin lungs Rightatrium Leftatrium Figure 20-1 An Overview of the Cardiovascular System. Rightventricle Leftventricle Capillariesin trunkandlower limbs

  7. An Introduction to the Cardiovascular System • Four Chambers of the Heart • Rightatrium • Collects blood from systemic circuit • Rightventricle • Pumps blood to pulmonary circuit • Leftatrium • Collects blood from pulmonary circuit • Leftventricle • Pumps blood to systemic circuit

  8. 20-1 Anatomy of the Heart • The Heart • Great veins and arteries at the base • Pointed tip is apex • Surrounded by pericardial sac • Sits between two pleural cavities in the mediastinum

  9. 20-1 Anatomy of the Heart • The Pericardium • Double lining of the pericardial cavity • Visceralpericardium • Inner layer of pericardium • Parietalpericardium • Outer layer • Forms inner layer of pericardialsac

  10. 20-1 Anatomy of the Heart • The Pericardium • Pericardial cavity • Is between parietal and visceral layers • Contains pericardialfluid • Pericardial sac • Fibrous tissue • Surrounds and stabilizes heart

  11. 20-1 Anatomy of the Heart • Superficial Anatomy of the Heart • Atria • Thin-walled • Expandable outer auricle (atrialappendage) • Sulci • Coronarysulcus divides atria and ventricles • Anteriorinterventricularsulcus and posteriorinterventricularsulcus • Separate left and right ventricles • Contain blood vessels of cardiac muscle

  12. Base of heart 1 1 Ribs 2 2 3 3 4 4 5 5 6 Figure 20-3a The Position and Superficial Anatomy of the Heart. 6 7 7 Apex of heart 8 8 9 a 9 10 10 Heart position relative to the rib cage.

  13. Figure 20-3b The Position and Superficial Anatomy of the Heart.

  14. Figure 20-3d The Position and Superficial Anatomy of the Heart.

  15. 20-1 Anatomy of the Heart • The Heart Wall • Epicardium • Visceral pericardium • Covers the heart • Myocardium • Muscular wall of the heart • Concentric layers of cardiac muscle tissue • Atrial myocardium wraps around great vessels • Two divisions of ventricular myocardium • Endocardium • Simple squamous epithelium

  16. Figure 20-4a The Heart Wall. Pericardialcavity Parietalpericardium Myocardium(cardiac muscle tissue) Dense fibrous layer Cardiac muscle cells Areolar tissue Connective tissues Mesothelium Artery Vein Endocardium Epicardium(visceralpericardium) Endothelium Areolar tissue Mesothelium Areolar tissue Heart wall a A diagrammatic section through the heartwall, showing the relative positions of theepicardium, myocardium, and endocardium.The proportions are not to scale; thethickness of the myocardial wall has beengreatly reduced.

  17. Atrialmusculature Ventricularmusculature Figure 20-4b The Heart Wall. Cardiac muscle tissueforms concentric layers thatwrap around the atria or spiralwithin the walls of the ventricles. b

  18. 20-1 Anatomy of the Heart • Cardiac Muscle Tissue • Intercalateddiscs • Interconnect cardiacmusclecells • Secured by desmosomes • Linked by gap junctions • Convey force of contraction • Propagate action potentials

  19. 20-1 Anatomy of the Heart • Characteristics of Cardiac Muscle Cells • Small size • Single, central nucleus • Branching interconnections between cells • Intercalated discs

  20. Table 20-1 Structural and Functional Differences between Cardiac Muscle Cells and Skeletal Muscle Fibers.

  21. 20-1 Anatomy of the Heart • Internal Anatomy and Organization • Inter-atrialseptum separates atria • Inter-ventricularseptum separates ventricles

  22. 20-1 Anatomy of the Heart • Internal Anatomy and Organization • Atrioventricular (AV) valves • Connect right atrium to right ventricle and left atrium to left ventricle • Are folds of fibrous tissue that extend into openings between atria and ventricles • Permit blood flow in one direction • From atria to ventricles

  23. 20-1 Anatomy of the Heart • The Right Atrium • Superiorvenacava • Receives blood from head, neck, upper limbs, and chest • Inferiorvenacava • Receives blood from trunk, viscera, and lower limbs • Coronarysinus • Cardiac veins return blood to coronary sinus • Coronary sinus opens into right atrium

  24. 20-1 Anatomy of the Heart • The Right Atrium • Foramenovale • Before birth, is an opening through interatrial septum • Connects the two atria • Seals off at birth, forming fossaovalis • Pectinatemuscles • Contain prominent muscular ridges • On anterior atrial wall and inner surfaces of right auricle

  25. 20-1 Anatomy of the Heart • The Right Ventricle • Free edges attach to chordaetendineae from papillarymuscles of ventricle • Prevent valve from opening backward • Rightatrioventricular (AV) valve • Also called tricuspidvalve • Opening from right atrium to right ventricle • Has three cusps • Prevents backflow

  26. 20-1 Anatomy of the Heart • The Right Ventricle • Trabeculaecarneae • Muscular ridges on internal surface of right (and left) ventricle • Includes moderatorband • Ridge contains part of conductingsystem • Coordinates contractions of cardiac muscle cells

  27. 20-1 Anatomy of the Heart • The Pulmonary Circuit • Conusarteriosus (superior end of right ventricle) leads to pulmonarytrunk • Pulmonary trunk divides into left and rightpulmonaryarteries • Blood flows from right ventricle to pulmonary trunk through pulmonaryvalve • Pulmonary valve has three semilunar cusps

  28. 20-1 Anatomy of the Heart • The Left Atrium • Blood gathers into left and rightpulmonaryveins • Pulmonary veins deliver to left atrium • Blood from left atrium passes to left ventricle through left atrioventricular (AV) valve • A two-cusped bicuspidvalve or mitralvalve

  29. 20-1 Anatomy of the Heart • The Left Ventricle • Holds same volume as right ventricle • Is larger; muscle is thicker and more powerful • Similar internally to right ventricle but does not have moderator band

  30. 20-1 Anatomy of the Heart • The Left Ventricle • Systemic circulation • Blood leaves left ventricle through aorticvalve into ascendingaorta • Ascending aorta turns (aorticarch) and becomes descendingaorta

  31. 20-1 Anatomy of the Heart • Structural Differences between the Left and Right Ventricles • Right ventricle wall is thinner, develops less pressure than left ventricle • Right ventricle is pouch-shaped, left ventricle is round

  32. 20-1 Anatomy of the Heart • The Heart Valves • Two pairs of one-way valves prevent backflow during contraction • Atrioventricular (AV) valves • Between atria and ventricles • Blood pressure closes valve cusps during ventricular contraction • Papillary muscles tense chordae tendineae to prevent valves from swinging into atria

  33. 20-1 Anatomy of the Heart • The Heart Valves • Semilunar valves • Pulmonary and aortic tricuspid valves • Prevent backflow from pulmonary trunk and aorta into ventricles • Have no muscular support • Three cusps support like tripod

  34. 20-1 Anatomy of the Heart • AorticSinuses • At base of ascending aorta • Sacs that prevent valve cusps from sticking to aorta • Origin of right and left coronary arteries

  35. 20-1 Anatomy of the Heart • Connective Tissues and the Cardiac Skeleton • Connective tissue fibers • Physically support cardiac muscle fibers • Distribute forces of contraction • Add strength and prevent overexpansion of heart • Provide elasticity that helps return heart to original size and shape after contraction

  36. 20-1 Anatomy of the Heart • The CardiacSkeleton • Four bands around heart valves and bases of pulmonary trunk and aorta • Stabilize valves • Electrically insulate ventricular cells from atrial cells

  37. 20-1 Anatomy of the Heart • The Blood Supply to the Heart • = Coronarycirculation • Supplies blood to muscle tissue of heart • Coronary arteries and cardiac veins • The CoronaryArteries • Left and right • Originate at aortic sinuses • High blood pressure, elastic rebound forces blood through coronary arteries between contractions

  38. 20-1 Anatomy of the Heart • RightCoronaryArtery • Supplies blood to: • Right atrium • Portions of both ventricles • Cells of sinoatrial (SA) and atrioventricular nodes • Marginalarteries (surface of right ventricle) • Posterior interventricular artery • Left Coronary Artery • Supplies blood to: • Left ventricle • Left atrium • Interventricular septum

  39. 20-1 Anatomy of the Heart • Two Main Branches of Left Coronary Artery • Circumflexartery • Anteriorinterventricularartery • ArterialAnastomoses • Interconnect anterior and posterior interventricular arteries • Stabilize blood supply to cardiac muscle

  40. 20-1 Anatomy of the Heart • The Cardiac Veins • Greatcardiacvein • Drains blood from area of anterior interventricular artery into coronary sinus • Anterior cardiac veins • Empty into right atrium • Posteriorcardiacvein, middlecardiacvein, and smallcardiacvein • Empty into great cardiac vein or coronary sinus

  41. Aorticarch Left coronary artery Pulmonarytrunk Ascendingaorta Circumflexartery Rightcoronaryartery Anteriorinterventricularartery Atrialarteries Greatcardiacvein Figure 20-9a The Coronary Circulation. Anteriorcardiacveins Smallcardiac vein Marginal artery Coronary vessels supplying and draining the anteriorsurface of the heart. a

  42. Coronary sinus Circumflex artery Great cardiac vein Marginal artery Posteriorinterventricularartery Posteriorcardiacvein Smallcardiacvein Figure 20-9b The Coronary Circulation. Leftventricle Rightcoronaryartery Marginal artery Middle cardiac vein b Coronary vessels supplying and drainingthe posterior surface of the heart.

  43. Narrowing of Artery Normal Artery Tunicaexterna Lipid depositof plaque Tunicamedia Figure 20-10 Heart Disease and Heart Attacks (Part 2 of 4). Cross section Cross section

  44. 20-1 Anatomy of the Heart • Heart Disease – Coronary Artery Disease • Coronaryarterydisease (CAD) • Areas of partial or complete blockage of coronary circulation • Cardiac muscle cells need a constant supply of oxygen and nutrients • Reduction in blood flow to heart muscle produces a corresponding reduction in cardiac performance • Reduced circulatory supply, coronaryischemia, results from partial or complete blockage of coronary arteries

  45. 20-1 Anatomy of the Heart • Heart Disease – Coronary Artery Disease • Usual cause is formation of a fatty deposit, or atheroscleroticplaque, in the wall of a coronary vessel • The plaque, or an associated thrombus (clot), then narrows the passageway and reduces blood flow • Spasms in smooth muscles of vessel wall can further decrease or stop blood flow • One of the first symptoms of CAD is commonly anginapectoris

  46. 20-1 Anatomy of the Heart • Heart Disease – Coronary Artery Disease • Anginapectoris • In its most common form, a temporary ischemia develops when the workload of the heart increases • Although the individual may feel comfortable at rest, exertion or emotional stress can produce a sensation of pressure, chest constriction, and pain that may radiate from the sternal area to the arms, back, and neck

  47. 20-1 Anatomy of the Heart • Heart Disease – Coronary Artery Disease • Myocardialinfarction (MI), or heartattack • Part of the coronary circulation becomes blocked, and cardiac muscle cells die from lack of oxygen • The death of affected tissue creates a nonfunctional area known as an infarct • Heart attacks most commonly result from severe coronary artery disease (CAD)

  48. 20-1 Anatomy of the Heart • Heart Disease – Coronary Artery Disease • Myocardialinfarction (MI), or heartattack • Consequences depend on the site and nature of the circulatory blockage • If it occurs near the start of one of the coronary arteries: • The damage will be widespread and the heart may stop beating • If the blockage involves one of the smaller arterial branches: • The individual may survive the immediate crisis but may have many complications such as reduced contractility and cardiac arrhythmias

  49. 20-1 Anatomy of the Heart • Heart Disease – Coronary Artery Disease • Myocardialinfarction (MI), or heartattack • A crisis often develops as a result of thrombus formation at a plaque (the most common cause of an MI), a condition called coronarythrombosis • A vessel already narrowed by plaque formation may also become blocked by a sudden spasm in the smooth muscles of the vascular wall • Individuals having an MI experience intense pain, similar to that felt in angina, but persisting even at rest

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