The Circulatory System

1. The Circulatory System The Heart Lecture # 3 Part 1 (Chapter 19) • Overview of Cardiovascular System • Gross Anatomy of the Heart • Cardiac Conduction System and Cardiac Muscle • Electrical and Contractile Activity of Heart

2. -Blood It is the liquid medium in which these substance travel. The Circulatory System -Cardiovascular System Blood vessels They ensure the proper routing of blood to its destination. It transports substances from place to place in the body. Heart It is the pump that keeps the blood flowing.

3. Systemic Circuit It supplies blood to every organ of the body, including the heart itself. Cardiovascular System Pulmonary Circuit It carries blood to the lungs for gas exchange and returns it to the heart. Aorta Pulmonary Pulmonary Vena cava Arteries (2) Veins (4) Blood Vessels Arteries They carry blood away from the heart. Veins They carry blood back to (toward) the heart. Capillaries They connect the arteries with the veins.

4. Gas exchange Pulmonary Circuit It carries blood to the lungs for gas exchange and returns it to the heart. O2rich blood through VEINS O2poor blood through ARTERIES Systemic Circuit It supplies blood to every organ of the body, including the heart itself. O2rich blood through ARTERIES O2poor blood through VEINS

5. GasExchange Pulmonary Systemic Circuit Capillary Circuit Lung Arteriole Venule Pulmonary arteries (2) Pulmonary veins (4) O2 rich, CO2 poor blood Wastes Nutrients O2 O2 CO2 CO2 Venae cavae Aorta Capillary Arteriole Venule Tissue O2 poor, CO2 rich blood

6. Position, Size, and Shape of the Heart The heart is located in the thoracic cavity, in the mediastinum, between the lungs. The base is the wide, superior portion of the heart, the great blood vessels attach here. The apex is the inferior end, tilts to the left. The heart is enclosed in the pericardium.

7. The Pericardium The pericardium is a double-walled sac (pericardial sac) that encloses the heart. • Superficial fibrous layer of connective tissue Parietal pericardium • Deep, thin serous layer. Visceral pericardium or epicardium Pericardial cavity It is the space inside the pericardial sac filled with 5-30 mL of pericardial fluid. Functions of the Pericardium: • 1- It allows the heart to beat without friction. • 2- It provides room to expand, yet resists excessive expansion. Pericarditis: It is the inflammation of the membranes. It produces a painful friction rub with each heartbeat.

8. The Heart Wall Epicardium (visceral pericardium) Myocardium Endocardium Epicardium (visceral pericardium) • It is a serous membrane covering heart. Also includes a thick layer of adipose tissue in some places. The coronary blood vessels travel through this layer. Myocardium • It is a layer of cardiac muscle proportional to work load. • It also contains a framework of collagen and elastic fibers, which: • - Provides structural support and attachment for cardiac muscle and anchor for valve tissue. - Is an electrical insulation between atria and ventricles, so the atria can not stimulate the ventricles directly. Endocardium • It is the smooth inner lining of heart and blood vessels. It covers the valve surfaces and is continuous with the endothelium of blood vessels.

9. The Heart Wall Parietal pericardium Pericardial cavity Areolar tissue Areolar tissue MYOCARDIUM (cardiac muscle tissue) ENDOCARDIUM EPICARDIUM Endothelium Mesothelium Visceral pericardium Mesothelium Areolar tissue Fibrous tissue Endocarditis is the inflammation of the inside lining of the heart chambers and heart valves (endocardium). Most people who develop endocarditis have heart disease of the valves.

10. The Heart Poor oxygen blood Gas exchange Superior vena cava Pulmonary arteries Coronary sinus Reach oxygen blood Pulmonary veins Inferior vena cava RIGHT ATRIUM LEFT ATRIUM To the rest of the body Aorta TISSUES RIGHT VENTRICLE LEFT VENTRICLE

11. Superior vena cava It drains oxygen-poor blood from tissues and organs superior to the diaphragm to the right atrium. Aorta Pulmonary trunk It carries oxygen-poor blood from the right ventricle to the lungs. It carries oxygen-rich blood from the left ventricle to the whole body. Pulmonary veins (4) Inferior vena cava It drains oxygen-poor blood from tissues and organs inferior to the diaphragm to the right atrium. They carry oxygen-rich blood from the lungs to the left atrium. Coronary sinus (no shown) It drains oxygen-poor blood from the heart tissues to the right atrium.

12. The Chambers of the Heart • Left auricle • Coronary or atrioventricular sulcus • Anterior interventricular sulcus Pectinate muscles Anterior view • Left atrium • Right atrium Trabeculae carneae • Left ventricle • Right ventricle • Coronary or atrioventricular sulcus • Posterior interventricular sulcus Interatrial septum Interventricular septum Posterior view

13. Blood Flow Through Heart Chambers Aorta Pulmonary trunk Superior vena cava • Left atrium It receives blood returning from the lungs through the pulmonary veins (4). Pulmonary arteries Pulmonary veins • Right atrium Pulmonary veins It receives O2 poor blood returning to the heart through the superior and inferior vena cava and the coronary sinus (no shown). • Left ventricle It pumps O2 rich blood through the aorta artery to every organ of the body. Inferior vena cava It pumps O2 poor blood to the lungs through the pulmonary arteries. • Right ventricle

14. The valves ensure a one-way flow, by preventing back flow of the blood. The Valves Left AV (bicuspid or mitral) valve Right AV (tricuspid) valve It prevents back flow of blood from the aorta to the LV Pulmonary semilunar valve Pulmonary semilunar valve Left AV (bicuspid) valve It prevents back flow of blood from the pulmonary trunk to the RV Aortic semilunar valve It prevents back flow of blood from the LV to the LA Right AV (tricuspid) valve Aortic semilunar valve It prevents back flow of blood from the RV to the RA Chordae tendineae Papillary muscles

15. Blood Flow Through Heart Chambers

16. Endoscopic photo of the aortic valve, viewed from above. Papillary muscles and tendinous cords seen from within the right ventricle.

17. The Coronary Circulation If you heart lasts 80 years and beats an average of 75 times a minute, it will be beat more than 3 000 000 000 times and pump more than 200 000 000 liters of blood. The heart is a remarkable hardworking organ and needs an abundant supply of O2. The blood vessels of the heart wall constitute the coronary circulation. A polymer cast of the coronary circulation. The coronary circulation supplies the myocardium with about 250 mL of blood per minute.

18. The Coronary Circulation Left coronary artery (LCA) Right coronary artery (RCA) Circumflex branch of LCA • It supplies right atrium and sinoatrial node (pacemaker). • It supplies left atrium and posterior wall of left ventricle. Right marginal branch of RCA Anterior interventricular branch of LCA • It supplies lateral aspect of right atrium and ventricle. • It supplies both ventricles and anterior two-thirds of the inter-ventricular septum. Posterior interventricular branch of RCA • It supplies posterior walls of ventricles. Left marginal branch of LCA • It supplies posterior wall of left ventricle. Great cardiac vein Anterior view

19. The Coronary Circulation Coronary sinus • It collects blood and empties into right atrium. Left marginal vein Posterior interventricular vein or middle cardiac vein Posterior interventricular branch of RCA Right coronary artery (RCA) Left marginal branch of LCA Posterior view Right marginal branch of RCA

20. The Circulatory System The Heart Lecture # 3 Part 2 (Chapter 19) • Overview of Cardiovascular System • Gross Anatomy of the Heart • Cardiac Conduction System and Cardiac Muscle • Electrical and Contractile Activity of Heart

21. Conduction System • It is composed of an internal pacemaker and nervelike conduction pathways through myocardiumthat generate and conduct rhythmic electrical signals. Sinoatrial node (pacemaker) Atrioventricular bundle • It initiates each heartbeat and determines heart rate. It is a pathway by which the signals leave the AV node. Atrioventricular node • It acts as insulator to prevent currents from getting to the ventricles from any other route, and delays the electrical excitation. Left bundle branch Right bundle branch They distribute the electrical excitation to the cardiocytes of the ventricles. Purkinje fibers Purkinje fibers

22. Cardiac Conduction System

24. DEPOLARIZATION Gated sodium channels are open Outside positive Outside positive Outside positive -70 mV -70 mV -65 mV -65 mV Outside positive Inside positive Depolarization Resting potential HYPERPOLARIZATION Gated Potassium channels are open Outside positive Outside positive -80 mV -70 mV Inside negative -70 mV -80 mV Hyperpolarization Resting potential

25. Action Potential Pacemaker Potential Resting Potential Fast K+ outflow Fast Ca+ and Na+ inflow -60 mV -60 mV -40 mV Slow Na+ inflow SA node does not have a stable resting membrane potential. It starts at -60 mV. • It drifts upward because of a slow inflow of Na+. • When it reaches a threshold of -40 mV, voltage-gated Ca2+ and Na+ channels open and a faster depolarization occurs peaking at 0 mV. • The K+ channels then open and K+ leaves the cell causing repolarization. Action Potentials: They are changes in the transmembrane potential that, once initiated, affect an entire excitable membrane Each depolarization of the SA node sets off one heartbeat. At rest, fires every 0.8 seconds or 75 bpm

26. The Electrocardiogram R • An ECG is a composite of all action potentials of nodal and myocardial cells, detected, amplified and recorded by electrodes on arms, legs and chest. QRS complex +1 Depolarization of ventricles Depolarization of atria T P Repolarization of ventricles 0 Q S PQ segment ST segment It represents the time during which the ventricles contract and eject blood Millivolts 100 msec Atrial systole Ventricular systole

27. 0.8 second R QRS complex +1 PQ segment ST segment T wave P wave Millivolts 0 PR interval Q S QT interval QRS interval –1

28. 1- Atrial depolarization begins. 2- Atrial depolarization complete (atria contracted). 3- Ventricles begin to depolarize at apex; atria repolarize (atria relaxed). 4- Ventricular depolarization complete (ventricles contracted). 5- Ventricular repolarization begins at apex (ventricles begin relaxation). 6- Ventricular repolarization complete (ventricles relaxed).

29. The Cardiac Rhythm Sinus rhythm: It is the normal heartbeat triggered by the SA node. At rest, the sinus rhythm is about 70 to 80 times per minute (rates from 60 to 100 bpm). Tachycardia: It is a persistent, resting adult heart rate above 100 bpm. Bradycardia: It is a persistent, resting adult heart rate below 60 bpm. Extra-systoles: Extra heart beats produced in any region of spontaneous firing other than the SA node. If the SA node is damaged, other part of the myocardium may take over the governance of the heart rhythm. Ectopic focus: Any region of spontaneous firing other than the SA node. The most common ectopic focus is the AV node, which produces a nodal rhythm. It is the cardiac rhythm produced by the AV node. It is a slower heartbeat of 40 to 50 bpm. Nodal rhythm: If neither the SA nor AV nodes is functioning, an artificial pacemaker is required. It is any abnormal cardiac rhythm. Arrhythmia: Heart block: It is the failure of any part of the of the cardiac conducting system to transmit signals.

30. 0.8 sec 0.5 sec 75 bpm Sinus Rhythm (normal) 120 bpm Tachycardia 1.4sec 1.4sec 0.5 sec 0.3 sec 1.4sec 46 bpm Bradycardia Arrhythmia Extrasystole Nodal Rhythm Ventricular fibrillation Heart block