1. 1 Chapter 18 Anatomy of the Cardiovascular System

2. 2 Heart Location of the heart –Lies in the mediastinum –Posteriorly the heart rests on the bodies of thoracic vertebrae 5 through 8 –Boundaries of the heart are clinically important as an aid in diagnosing heart disorders

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4. 4 Heart Size and shape of the heart –At birth, is transverse and appears large in proportion to diameter of chest cavity, 1/130 body weight –Between puberty and 25 years of age the heart attains its adult shape and weight, 1/300 body weight –Males- 310 g –Females- 225 g

5. 5 Heart: Structure Pericardium- covers the heart –Function of the heart coverings—provides protection against friction pericardium from a normal ferret

6. 6 Heart: Structure –Wall of the heart—made up of three distinct layers: Epicardium –outer layer of heart wall Myocardium –thick, contractile middle layer of heart wall –compresses the heart cavities, and the blood within them, with great force Endocardium –delicate inner layer of endothelial tissue

7. 7 Heart: Structure Chambers of the heart— divided into four cavities with the right and left chambers separated by the septum Atria –Two superior chambers, known as “receiving chambers,” because they receive blood from veins –Myocardial wall of each atrium is not very thick, because little pressure is needed to move blood such a small distance

8. 8 Heart: Structure Ventricles –Two lower chambers, known as “pumping chambers,” because they push blood into the large network of vessels –Ventricular myocardium is thicker than myocardium of the atria, because great force must be generated to pump blood a large distance (to lungs and body) –myocardium of left ventricle is thicker than the right, because it must push blood much further

9. 9 Right Atrium Left Atrium Right Ventricle Left Ventricle Lungs Pulmonary Artery Through bicuspid valve Body Pulmonary Vein Through tricuspid (mitral) valve Aorta Superior Vena Cava

10. 10 To Body To Lungs To Brain Right Ventricle to the LUNGS (blue chambers) Left Ventricle to the BODY (red chambers) Brain & Body  Right Atrium  Right Ventricle  Lungs  Left Atrium  Left Ventricle  Brain & Body

11. 11 Heart: Valves Valves of the heart— devices that permit the flow of blood in one direction only Atrioventricular (AV) valves—prevent blood from flowing back into the atria from the ventricles when the ventricles contract –Tricuspid valve (LEFT AV valve)— guards the left atrioventricular orifice with 3 flaps of endocardium –Bicuspid, valve (RIGHT AV valve)—similar in structure to tricuspid valve except only two flaps present

12. 12 Heart: Valves Semilunar (SL) valves –half moon–shaped flaps growing out from the lining of the pulmonary artery and aorta –prevents blood from flowing back into ventricles from aorta and pulmonary artery

13. 13 Heart: Blood Supply Artery: Carries blood AWAY from heart –Coronary arteries –First branches to come off aorta –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 –Most abundant blood supply goes to myocardium of left ventricle

14. 14 Heart: Blood Supply Veins of the coronary circulation –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 –Several veins drain directly into right atrium

15. 15 Heart –Conduction system of the heart Sinoatrial node (SA node or pacemaker)— hundreds of cells in right atrial wall near opening of superior vena cava- start heart beat Atrioventricular node (AV node)—small mass of special cardiac muscle in right atrium along lower part of interatrial septum Atrioventricular bundle (bundle of His) and Purkinje fibers –Bundle of His originates in AV node, extends by two branches down the two sides of the interventricular septum, and continues as Purkinje fibers –Purkinje fibers extend out to papillary muscles and lateral walls of ventricles

16. 16 Heart –Nerve supply of the heart Cardiac plexuses— made up of the combination of excitatory and inhibitory fibers Vagus fibers— inhibitory, or depressor, nerves

17. 17 Blood Vessels –Arteries Carry blood AWAY from heart—all arteries (except pulmonary artery) carry oxygenated blood Elastic arteries— largest in body –Examples: aorta and its major branches –Able to stretch without injury –Accommodate surge of blood when heart contracts and able to recoil when ventricles relax

18. 18 Blood Vessels –Arteries Muscular (distributing) arteries –Smaller in diameter than elastic arteries –Muscular layer is thick »Examples: brachial, gastric, superior mesenteric Arterioles (resistance vessels) –Smallest arteries –Important in regulating blood flow to organs

19. 19 Blood Vessels –Capillaries— primary exchange vessels Microscopic vessels Carry blood from arterioles to venules Not evenly distributed –highest numbers in tissues with high metabolic rate may be absent in some “avascular” tissues such as cartilage

20. 20 Blood Vessels Types of capillaries –True capillaries –Continuous capillaries –Fenestrated capillaries –Sinusoids

21. 21 Blood Vessels –Veins Carry blood toward the heart Act as collectors and as reservoir vessels called capacitance vessels

22. 22 Circulatory routes –Systemic circulation- Left Ventricle  Brain & Body  Right Atrium –Pulmonary circulation- Right Atrium  Right Ventricle  Lungs  Left Atrium

23. 23 Systemic circulation –Systemic arteries arteries  arterioles  capillaries

24. 24 Fetal circulation Basic plan of fetal circulation— additional vessels needed to allow fetal blood to secure oxygen from maternal blood at the placenta Umbilical vein- returns oxygenated blood from placenta to fetus Foramen ovale- opening in septum between right and left atria

25. 25 Changes in circulation at birth 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 Foramen ovale—functionally closed shortly after a newborn’s first breath and pulmonary circulation is established; structural closure takes approximately 9 months Ductus arteriosus—contracts with establishment of respiration, becomes ligamentum arteriosum Fetal circulation

26. 26 Cycle of Life: Cardiovascular Anatomy Birth— change from placenta-dependent system Heart and blood vessels maintain basic structure and function from childhood through adulthood –Exercise thickens myocardium and increases supply of blood vessels in skeletal muscle tissue Adulthood through later adulthood—degenerative changes –Atherosclerosis— blockage or weakening of critical arteries –Heart valves and myocardial tissue degenerate— reduces pumping efficiency