1. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: Cardiovascular system Chapter objectives: –To learn the structures of the heart and their functions –To understand the heart’s conduction system –To learn about the flow of blood through the heart and body

2. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: Cardiovascular system Functions: –Supply life-sustaining oxygen and nutrients to the body’s cells –Remove metabolic waste products –Carry hormones from one part of the body to another Structures: –Heart –Blood vessels –Lymphatics

3. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: Cardiovascular system Heart Lies beneath the sternum in the mediastinum, between the 6 th and 7 th ribs Consists of two pumps: the right side pumps blood to the lungs, and the left side pumps blood to the rest of the body Heart structure –Pericardium—sac surrounding the heart Consists of fibrous pericardium (tough, white, fibrous tissue) and serous pericardium (thin, smooth inner portion) Pericardial space—space between the fibrous and serous pericardia; contains pericardial fluid, which lubricates the heart

4. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: Cardiovascular system Heart Heart structure (continued) –Heart wall Epicardium—outer layer Myocardium—middle layer Endocardium—inner layer –Heart chambers Right atrium—receives blood from the superior and inferior venae cavae Left atrium—receives blood from the two pulmonary veins

5. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: Cardiovascular system Heart –Heart chambers (continued) Interatrial septum—separates the right and left atria Right ventricle—pumps blood to the lungs Left ventricle—pumps blood to all other vessels in the body Interventricular septum—separates the right and left ventricles

6. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: Cardiovascular system Heart –Heart valves Atrioventricular valves: –Tricuspid valve—prevents backflow from the right ventricle into the right atrium –Mitral valve—prevents backflow from the left ventricle into the left atrium Semilunar valves: –Pulmonic valve—prevents backflow from the pulmonary artery into the right ventricle –Aortic valve: prevents backflow from the aorta into the left ventricle

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8. Chapter 8: Cardiovascular system Heart Conduction system –Causes blood to move throughout the body –Pacemaker cells—specialized cells in the heart with unique characteristics: Automaticity—ability to generate an electrical impulse automatically Conductivity—ability to pass the impulse to the next cell Contractility—ability to shorten fibers in the heart when receiving the impulse

9. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: Cardiovascular system Heart Conduction system (continued) –Sinoatrial (SA) node—normal pacemaker of the heart; results in atrial contraction; generates 60-100 impulses/minute –Atrioventricular (AV) node—slows the impulse between the atria and ventricles, allowing time for blood filling before ventricular contraction –Bundle of His—conducts the impulse from the AV node; branches off into right and left bundles –Purkinje fibers—distal portions of the right and left bundles; initiate contraction of the ventricles

10. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: Cardiovascular system Heart Conduction system (continued) –Safety system SA node fails to fire—AV node generates 40-60 impulses/minute SA and AV nodes fail—ventricles generate 20-40 impulses/minute

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12. Chapter 8: Cardiovascular system Heart Cardiac cycle –Period from the beginning of one heartbeat to the beginning of the next –Electrical and mechanical events occur in sequence and to proper degree to provide blood flow –Systole—ventricular contraction –Diastole—recovery period

13. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: Cardiovascular system Conduction system Cardiac cycle (continued) –Cardiac output—amount of blood the heart pumps in 1 minute –Stroke volume—amount of blood ejected with each heartbeat; affected by: Preload—stretching of muscle fibers in the ventricles Contractility—ability of the myocardium to contract normally Afterload—pressure needed to overcome the pressure in the aorta

14. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: Cardiovascular system Conduction system Cardiac cycle (continued) –Events of cycle Isovolumetric ventricular contraction—tension in the ventricles increases; AV valves close Ventricular ejection—ventricular pressure exceeds aortic and pulmonary arterial pressures; semilunar valves open; blood is ejected Isovolumetric relaxation—all valves are closed Ventricular filing—AV valves open; ventricles fill 70% Atrial systole (“atrial kick”)—adds additional 30% of blood to ventricles

15. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: Cardiovascular system Blood flow Blood vessels –Five types: Arteries—thick, muscular walls; accommodate higher speed blood flow and pressure Arterioles—thinner walls than arteries; constrict or dilate to control blood flow to capillaries Capillaries—have walls made up of a single layer of endothelial cells Venules—thin walls; gather blood from the capillaries Veins—thin walls but large diameters; return blood to the heart

16. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins

17. Chapter 8: Cardiovascular system Blood flow Circulation –Three methods to transport blood through the body: Pulmonary—unoxygenated blood travels from the right atrium via the pulmonary arteries, exchanges carbon dioxide for oxygen at the alveoli level, and transports oxygenated blood to the left atrium via the pulmonary veins Systemic—oxygenated blood is ejected from the left ventricle to the aorta, which branches off to other vessels to transport blood to organs

18. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: Cardiovascular system Blood flow Circulation (continued) Coronary—blood flows out of the heart during diastole and through the cardiac arteries to nourish heart muscle

19. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins Chapter 8: Cardiovascular system Blood flow –Coronary vessels Right coronary artery—supplies the right atrium, most of the right ventricle, and the inferior part of the left ventricle Left coronary artery—splits into the anterior descending artery and circumflex artery; supplies the left atrium, most of the left ventricle, and most of the interventricular septum Coronary sinus—largest coronary vein; opens into the right atrium; most coronary veins empty into it Anterior cardiac veins—do not empty into the coronary sinus; empty into the right atrium

20. Copyright © 2013 Wolters Kluwer Health | Lippincott Williams & Wilkins