1. Anatomy of the Cardiovascular System Chapter 18 pages 677 - 724

2. Heart Location of the heart Location of the heart Lies in the mediastinum Lies in the mediastinum ribs 2 through 6 ribs 2 through 6 approximately two thirds of its mass is to the left of the midline approximately two thirds of its mass is to the left of the midline Apex lies on the diaphragm, pointing to the left Apex lies on the diaphragm, pointing to the left Base lies just below the second rib Base lies just below the second rib Boundaries of the heart are clinically important as an aid in diagnosing heart disorders Boundaries of the heart are clinically important as an aid in diagnosing heart disorders

3. Coverings of the heart Pericardium Pericardium Fibrous pericardium tough, loose-fitting inextensible sac tough, loose-fitting inextensible sac Serous pericardium parietal layer lies inside fibrous pericardium parietal layer lies inside fibrous pericardium visceral layer (epicardium) adheres to outside of the heart visceral layer (epicardium) adheres to outside of the heart provides protection against friction provides protection against friction

4. Layers of the heart Epicardium Epicardium outer layer of heart wall outer layer of heart wall Myocardium Myocardium thick, contractile middle layer of heart wall thick, contractile middle layer of heart wall compresses the heart cavities, and the blood within them, with great force compresses the heart cavities, and the blood within them, with great force Endocardium Endocardium delicate inner layer of endothelial tissue delicate inner layer of endothelial tissue

5. Chambers of the heart Atria (2) Atria (2) “ receiving chambers ” “ receiving chambers ” because they receive blood from veins because they receive blood from veins Myocardial wall of each atrium is not very thick Myocardial wall of each atrium is not very thick

6. Chambers of the heart Ventricles Ventricles “ pumping chambers ” “ pumping chambers ” because they push blood into the large network of vessels because they push blood into the large network of vessels Ventricular myocardium is very thick Ventricular myocardium is very thick because great force must be generated to pump blood a large distance because great force must be generated to pump blood a large distance myocardium of left ventricle is thicker than the right myocardium of left ventricle is thicker than the right because it must push blood much further because it must push blood much further

7. Heart Valves Atrioventricular (AV) valves prevent blood from flowing back into the atria from the ventricles when the ventricles contract prevent blood from flowing back into the atria from the ventricles when the ventricles contract Tricuspid valve (right AV valve) guards the right atrioventricular orifice guards the right atrioventricular orifice free edges of three flaps of endocardium are attached to papillary muscles by chordae tendineae free edges of three flaps of endocardium are attached to papillary muscles by chordae tendineae Bicuspid, or mitral, valve (left AV valve) similar in structure to tricuspid valve except only two flaps present similar in structure to tricuspid valve except only two flaps present

8. Heart Valves Semilunar (SL) valves Half-moon shaped valves that prevent back flow into the heart Half-moon shaped valves that prevent back flow into the heart Pulmonary semilunar valve Pulmonary semilunar valve at entrance of pulmonary artery at entrance of pulmonary artery Aortic semilunar valve Aortic semilunar valve at entrance of aorta at entrance of aorta

9. Blood supply of heart tissue Myocardial cells receive blood from right and left coronary arteries Myocardial cells receive blood from right and left coronary arteries First branches to come off aorta First branches to come off aorta Ventricles receive blood from branches of both right and left coronary arteries Ventricles receive blood from branches of both right and left coronary arteries Each ventricle receives blood only from a small branch of corresponding coronary artery Each ventricle receives blood only from a small branch of corresponding coronary artery Most abundant blood supply goes to myocardium of left ventricle Most abundant blood supply goes to myocardium of left ventricle The right coronary artery is dominant in approximately 50% of all hearts and the left in about 20%; in approximately 30%, neither coronary artery is dominant The right coronary artery is dominant in approximately 50% of all hearts and the left in about 20%; in approximately 30%, neither coronary artery is dominant http://www.youtube.com/watch?v=TS0Je1m9Q8A&feature=player_detailpagewww.youtube.com/watch?v=TS0Je1m9Q8A&feature=player_detailpage

10. Blood supply of heart tissue Veins of the coronary circulation Veins of the coronary circulation As a rule, veins follow a course that closely parallels that of coronary arteries As a rule, veins follow a course that closely parallels that of coronary arteries After going through cardiac veins, blood enters coronary sinus to drain into right atrium After going through cardiac veins, blood enters coronary sinus to drain into right atrium Several veins drain directly into right atrium Several veins drain directly into right atrium

11. Conduction system of the heart Key Components Key Components Sinoatrial node Sinoatrial node hundreds of cells in right atrial wall near opening of superior vena cava hundreds of cells in right atrial wall near opening of superior vena cava Atrioventricular node Atrioventricular node small mass of special cardiac muscle in right atrium along lower part of interatrial septum small mass of special cardiac muscle in right atrium along lower part of interatrial septum Atrioventricular bundle Atrioventricular bundle AV bundle originates in AV node, extends by two branches down the two sides of the interventricular septum AV bundle originates in AV node, extends by two branches down the two sides of the interventricular septum Purkinje fibers Purkinje fibers extend out to papillary muscles and lateral walls of ventricles extend out to papillary muscles and lateral walls of ventricles

12. Nerve supply of the heart Cardiac plexuses located near arch of aorta, made up of the combination of sympathetic and parasympathetic fibers Cardiac plexuses located near arch of aorta, made up of the combination of sympathetic and parasympathetic fibers Most fibers end in the SA node, but some end in the AV node and in the atrial myocardium Most fibers end in the SA node, but some end in the AV node and in the atrial myocardium Sympathetic nerves accelerator nerves Sympathetic nerves accelerator nerves Vagus fibers inhibitory, or depressor, nerves Vagus fibers inhibitory, or depressor, nerves

13. Blood Vessels Arteries Arteries Carry blood away from heart Carry blood away from heart Veins Veins Carry Blood toward the heart Carry Blood toward the heart Capillaries Capillaries Carry blood to cells of the body Carry blood to cells of the body

14. Arteries Elastic arteries Elastic arteries Able to stretch without injury Able to stretch without injury Accommodate surge of blood when heart contracts and able to recoil when ventricles relax Accommodate surge of blood when heart contracts and able to recoil when ventricles relax aorta and its major branches aorta and its major branches Muscular (distributing) arteries Muscular (distributing) arteries Smaller in diameter than elastic arteries Smaller in diameter than elastic arteries Muscular layer is thick Muscular layer is thick brachial, gastric brachial, gastric Arterioles (resistance vessels) Smallest arteries Important in regulating blood flow to end- organs Metarterioles Short connecting vessel between true arteriole and 20 to 100 capillaries Encircled by precapillary sphincters

15. Capillaries True capillaries True capillaries receive blood flowing from metarteriole with input regulated by precapillary sphincters receive blood flowing from metarteriole with input regulated by precapillary sphincters Continuous capillaries Continuous capillaries Continuous lining of endothelial cells Continuous lining of endothelial cells Openings called intercellular clefts exist between adjacent endothelial cells Openings called intercellular clefts exist between adjacent endothelial cells Fenestrated capillaries Fenestrated capillaries Have both intercellular clefts and “ holes ” to facilitate exchange functions Have both intercellular clefts and “ holes ” to facilitate exchange functions Sinusoids Sinusoids Large lumen and tortuous course Large lumen and tortuous course Absent or incomplete basement membrane Absent or incomplete basement membrane

16. Veins Veins Veins Carry blood toward the heart Carry blood toward the heart Act as collectors and as reservoir vessels Act as collectors and as reservoir vessels capacitance vessels capacitance vessels Types Types Veinules Veinules Veins Veins

17. Blood Vessel Layers Three Main layers Three Main layers Tunica adventitia Tunica adventitia found in arteries and veins found in arteries and veins Tunica media Tunica media found in arteries and veins found in arteries and veins Tunica intima Tunica intima found in all blood vessels found in all blood vessels only layer present in capillaries only layer present in capillaries

18. Building Blocks of Blood Vessels Lining endothelial cells Lining endothelial cells Only lining found in capillary Only lining found in capillary Line entire vascular tree Line entire vascular tree Provide a smooth luminal surface — protects against intravascular coagulation Provide a smooth luminal surface — protects against intravascular coagulation Capable of secreting a number of substances Capable of secreting a number of substances Capable of reproduction Capable of reproduction

19. Building Blocks of Blood Vessels Collagen fibers Collagen fibers Exhibit woven appearance Exhibit woven appearance Have only a limited ability to stretch (2% to 3%) under physiological conditions Have only a limited ability to stretch (2% to 3%) under physiological conditions Function to strengthen and keep lumen of vessel open Function to strengthen and keep lumen of vessel open

20. Building Blocks of Blood Vessels Elastic fibers Elastic fibers Fibers can stretch over 100% under physiological conditions Fibers can stretch over 100% under physiological conditions Play important role in creating passive tension to help regulate blood pressure throughout cardiac cycle Play important role in creating passive tension to help regulate blood pressure throughout cardiac cycle Smooth muscle fibers Smooth muscle fibers Present in all segments of vascular system except capillaries Present in all segments of vascular system except capillaries Most numerous in elastic and muscular arteries Most numerous in elastic and muscular arteries Exert active tension in vessels when contracting Exert active tension in vessels when contracting

21. Circulatory routes Systemic circulation Systemic circulation Left sided pump Left sided pump blood flows from the left ventricle of the heart through blood vessels to all parts of the body blood flows from the left ventricle of the heart through blood vessels to all parts of the body except gas exchange tissues of lungs except gas exchange tissues of lungs back to right atrium back to right atrium

22. Circulatory routes Pulmonary circulation Pulmonary circulation Right Sided pump Right Sided pump venous blood moves from right atrium to right ventricle to pulmonary artery to lung arterioles and capillaries venous blood moves from right atrium to right ventricle to pulmonary artery to lung arterioles and capillaries gases are exchanged gases are exchanged oxygenated blood returns to left atrium via pulmonary veins oxygenated blood returns to left atrium via pulmonary veins

23. Systemic circulation Arterial anastomosis Arterial anastomosis open into other branches of the same or other arteries open into other branches of the same or other arteries Arteriovenous anastomoses Arteriovenous anastomoses shunts occur when blood flows from an artery directly into a vein shunts occur when blood flows from an artery directly into a vein

24. Systemic circulation Superior Vena Cava Superior Vena Cava Venous blood from the head, neck, upper extremities, and thoracic cavity Venous blood from the head, neck, upper extremities, and thoracic cavity except lungs except lungs Inferior vena cava Inferior vena cava Venous blood from lower extremities and abdomen Venous blood from lower extremities and abdomen

25. Fetal circulation Two umbilical arteries Two umbilical arteries extensions of internal iliac arteries; extensions of internal iliac arteries; carry fetal blood to placenta carry fetal blood to placenta Placenta Placenta attached to uterine wall attached to uterine wall where exchange of oxygen and other substances between the separated maternal and fetal blood occurs where exchange of oxygen and other substances between the separated maternal and fetal blood occurs Umbilical vein Umbilical vein returns oxygenated blood from placenta to fetus returns oxygenated blood from placenta to fetus enters body through umbilicus continues as ductus venosus enters body through umbilicus continues as ductus venosus Ductus venosus continuation of umbilical vein, drains into inferior vena cava Foramen ovale opening in septum between right and left atria Ductus arteriosus small vessel connecting pulmonary artery with descending thoracic aorta

26. Diagram of Fetal Blood Flow

27. Fetal circulation Changes in circulation at birth Changes in circulation at birth When umbilical cord is cut, the two umbilical arteries, the placenta and the umbilical vein no longer function When umbilical cord is cut, the two umbilical arteries, the placenta and the umbilical vein no longer function Umbilical vein within the baby ’ s body becomes the round ligament of the liver Umbilical vein within the baby ’ s body becomes the round ligament of the liver Ductus venosus becomes the ligamentum venosum of the liver Ductus venosus becomes the ligamentum venosum of the liver Foramen ovale Foramen ovale functionally closed shortly after a newborn ’ s first breath and pulmonary circulation is established functionally closed shortly after a newborn ’ s first breath and pulmonary circulation is established structural closure takes approximately 9 months structural closure takes approximately 9 months Ductus arteriosus Ductus arteriosus contracts with establishment of respiration, becomes ligamentum arteriosum contracts with establishment of respiration, becomes ligamentum arteriosum

28. Changes over time Birth Birth change from placenta-dependent system change from placenta-dependent system Childhood to adulthood Childhood to adulthood Exercise thickens myocardium Exercise thickens myocardium increases blood supply increases blood supply Adulthood through later adulthood Adulthood through later adulthood degenerative changes degenerative changes Atherosclerosis Atherosclerosis blockage or weakening of critical arteries blockage or weakening of critical arteries Heart valves and myocardial tissue degenerate - reduces pumping efficiency Heart valves and myocardial tissue degenerate - reduces pumping efficiency