Cardiovascular System - Chapter 13 PDF

Chapter 13 Cardiovascular System  Cardiovascular System Cardiovascular System Consists of: Blood – Transport medium (cells suspended in fluid) Heart – Pump – drives circulation of blood Blood vessels – Tubing that conducts blood through circulation ...

Chapter 13 Cardiovascular System  Cardiovascular System Cardiovascular System Consists of: Blood – Transport medium (cells suspended in fluid) Heart – Pump – drives circulation of blood Blood vessels – Tubing that conducts blood through circulation  Blood Represents about 8% of total body weight Average blood volume= Consists of: 1. Erythrocytes Red blood cells 2. Leukocytes White blood cells 3. Platelets Cell fragments 4. Plasma=liquid portion of blood Comprised of: – Proteins -Hormones – Nutrients -Electrolytes  Plasma 55% of whole blood Buffy coat: Platelets platelets and Leukocytes leukocytes (white blood cells) Packed cell volume, or Erythrocytes Erythrocytes hematocrit (red blood (45% of whole cells) Blood)  Plasma Consists of: Water (90%) – dissolves materials (gases, nutrients, etc.) – acts as fluid for transport Proteins (7-9%) – Maintain osmotic pressure of blood albumins – Lipid transport – Immunity Antibodies – Clotting factors – Various enzymes  Formed Elements Erythrocytes – Red Blood Cells Leukocytes – White Blood Cells Fig 10.2 Thrombocytes – Platelets  Erythrocytes Red blood cells (RBCs) Contain hemoglobin – Function? No nucleus, organelles Structure – Biconcave discs Provides larger surface area for diffusion of O2 – Flexible membrane Allows RBCs to travel through narrow capillaries without rupturing in the process  Erythropoiesis Erythrocyte production RBCs survive about 120 days – Spleen removes most of old erythrocytes – Must be replaced at rate of 2-3 million cells/second Erythropoiesis occurs in bone marrow – Hematopoietic stem cells (HSC) – Multipotent  Erythropoiesis Role of Erythropoeitin (EPO) Figure 13.5  Anemia Refers to a below-normal O2-carrying capacity of the blood Causes of anemia – Dietary deficiencies – Blood Loss – Bone marrow failure – Hemolytic anemia  Platelets Thrombocytes Colorless cell fragments – Lack nuclei – Have organelles Come from Megakarocyte cell Function in hemostasis Thrombopoietin – Hormone produced by liver increases number of megakaryocytes and therefore increases platelet production  Hemostasis Hemostasis= – Prevents blood loss from a broken blood vessel Involves 3 major steps 1.Vascular spasm Reduces blood flow through a damaged vessel 2.Formation of a platelet plug Platelets aggregate on contact with exposed collagen in damaged wall of the vessel Platelets release ADP which causes surface of nearby circulating platelets to become sticky 3.Blood coagulation (clotting) Coagulation proteins in blood  Platelets At rest inhibited-why?àprostacyclin, nitric oxide Function – Formation of platelet plug – Activate clotting factors  Clot Formation Reinforces platelet plug by formation of clot Clotting factors are always present in blood plasma in inactive precursor form – Vessel damage that exposes collagen initiates cascade of reactions that involve successive activation of clotting factors Convert fibrinogen à fibrin  Blood Clot Formation Two pathways-Need both – Intrinsic pathway Activated by exposed collagen – Extrinsic pathway Released from damaged tissue Final Outcome – Fibrinogen (soluble) ® fibrin (insoluble)  Leukocytes White blood cells or WBCs Mobile units of body’s immune defense system Immune system – Recognizes and destroys or neutralizes materials within body that are foreign to “normal self” – Functions Defends against invading pathogens Identifies and destroys cancer cells that arise in body Functions as a “cleanup crew” that removes worn-out cells and tissue debris  Structure of the Heart Hollow, muscular organ Located in thoracic cavity 4 chambers – 2 Atria Fig 10.7 – 2 Ventricles Pumps constantly – variable rate Two Circuits – Pulmonary – Systemic  Heart Valves Two sets of valves 1. Atrioventricular (AV) valves 2. Semilunar valves Purpose Sounds  Blood Flow Through the Heart Deoxygenated blood enters right side through vena cavae →right atrium →right AV valve →right ventricle →pulmonary semilunar valve →pulmonary trunk and arteries →lungs (pulmonary circuit)  Blood Flow Through the Heart Oxygenated blood enters left side through pulmonary veins →left atrium →left AV valve →left ventricle →aortic semilunar valve →aorta →tissues (systemic circuit)  Cardiac Cycle Cardiac Cycle consists of 2 parts – Systole – Diastole  Cardiac Cycle Sequence of events – Systole 1. Isovolumetric contraction – Ventricles contract, but no blood ejected – Blood pressure rises above pressure in atria – Atrioventricular valves shut 2. Ejection – Blood pressure in ventricle exceeds pressure in arteries – Blood flows out of ventricles, causing pressure in ventricles to fall  Cardiac Cycle Sequence of Events – Diastole 1. Isovolumetric Relaxation – Pressure in ventricles drops below arterial pressure – Semilunar valves prevent backflow of blood Fig 10.10 – No change in ventricular volume 2. Rapid filling – Pressure in ventricles falls below atrial pressure – AV valves open, allowing blood to flow into ventricles 3. Atrial contraction  Electrical Activity of Heart Heart beats via autorhythmicity Two specialized types of cardiac muscle cells 1. Autorhythmic cells Do not contract Initiate AP's and spread impulse throughout heart 2. Contractile cells 99% of cardiac muscle cells Do mechanical work of pumping Normally do not initiate own action potentials  Electrical Activity of Heart Heart beats via autorhythmicity Two specialized types of cardiac muscle cells 1. Autorhythmic cells Do not contract Initiate AP's and spread impulse throughout heart 2. Contractile cells 99% of cardiac muscle cells Do mechanical work of pumping Normally do not initiate own action potentials  Electrical Activity of Heart Sequence – SA node Action potential spreads throughout right and left atria – AV node Conduction Delay Why? – Bundle of His – Purkinje fibers – Spread to non-conducting ventricular cells through gap junctions  Electrical Activity of Heart: Pacemaker Potential Mechanism of Autorhymicity SA node – Membrane permeability changes with AP Potassium – Sodium Calcium – Pacemaker Potential HCN channels Funny Channels Open when membrane potential hyperpolarizes – Depolarization due to Ca2+ Inherent rate~100 (not Na+) depolarizations/min  Electrical Activity of Heart: Myocardial Cells Electrical Activity of Contractile Cells Action Potential – Depolarization – Plateau – Repolarization  Excitation-Contraction Coupling in Cardiac Muscle Components of both skeletal and smooth muscle Gap Junctions located in intercalated discs  Electrical Activity of Heart Refractory Periods in Heart Why important? ECG Tracing  Electrocardiogram (ECG) Record of overall spread of electrical activity through heart Represents – Recording electrical activity of cardiac impulse that reaches body surface Not a direct recording of a single action potential in a single cell at a single point in time Uses? Figure 13.33b  Coronary Circulation Muscle is supplied with oxygen and nutrients by blood delivered to it by coronary circulation, not from blood within heart chambers Coronary vessels=provide blood supply to heart during diastole – During systole, coronary vessels are compressed by contracting heart muscle Coronary blood flow normally varies to keep pace with cardiac oxygen needs  Cardiovascular System Consists of – Heart – Blood – Blood Vessels  Vascular Tree Closed system of vessels – Pulmonary and Systemic Circuit Consists of – Arteries – Arterioles – Capillaries – Venules – Veins  Blood Vessels Both arteries and veins have similar layers – Tunica Externa – Tunica Media – Tunica Interna Differences  Arteries Take blood away from heart Function – Low resistance elastic conduits Due to large radius, arteries offer little resistance to blood flow – Pressure Reservoir Act as pressure reservoir to provide driving force for blood when heart is relaxing  Arterioles Function – Distribute cardiac output among systemic organs, depending on needs Vasoconstriction Vasodilation – Control by intrinsic and extrinsic factors  Constant pressure in pipe (mean arterial pressure) From pump (heart) High Moderate Low resistance resistance resistance No flow Moderate flow Large flow KEY Control valves = Arterioles  Capillaries Structure – Thin-walled, extensively branched Maximized surface area and minimized diffusion distance – Pre-capillary sphincters Function – Sites of exchange between blood and surrounding cells Only Tunica Intima  Types of Capillaries Continuous Fenestrated Discontinuous  Veins Function= – Return blood to heart – Blood reservoir Structure – Large radius offers little resistance to blood flow – Low Pressure System – Valves  Veins Problem with gravity  Veins Factors which enhance venous return – Driving pressure from cardiac contraction – Sympathetically induced venous vasoconstriction – Skeletal muscle activity – Effect of venous valves  Venous Return Venous Valves – prevent backflow of blood Skeletal Muscle Activity Fig 10.27 – contraction acts to “pump” veins – increases venous return with increased activity  Coronary Artery Disease (CAD) Leading cause of death in United States Pathophysiology – Atherosclerosis Risk Factors  Lymphatic System Carries Lymph – Where does lymph come from? Functions of lymphatic: 1. Aids immune system 2. Removal of interstitial fluid and return uni- directionally to heart 3. Absorbs and transports fatty acids  Importance of Lymphatic System Lack of function leads to edema Extreme example=Elephantiasis  For the Exam you Should be Able to: Define the components of the cardiovascular system Describe the components of blood Identify the formed elements of blood Describe the composition and function of plasma Describe a RBC Describe the regulation of red blood cell production Explain hemostasis and the role of platelets and coagulation proteins Differentiate between extrinsic pathway of coagulation and intrinsic pathway of coagulation  For the Exam you Should be Able to: Describe the structure of the heart, including valves, and blood flow through the heart Explain how valves open and close Distinguish between the systemic and the pulmonary circulation. Compare the two types of heart cells, including the electrical activity in each Describe the cardiac cycle in terms of systole and diastole Explain how the pressure differences within the heart chambers are responsible for blood flow during the cardiac cycle. Describe excitation-contraction coupling in heart muscle  For the Exam you Should be Able to: Describe the conduction system of the heart Explain an ECG, including the various waves, and uses Compare the structure and function of arteries, veins, and capillaries Explain the refractory period of the heart, and it’s importance Describe factors that contribute to venous return against gravity Define vasoconstriction and vasodilation Describe the three types of capillaries Explain the causes and risk factors of atherosclerosis. Explain how the lymph and lymphatic system relate to the blood and cardiovascular system.  For the Exam you Should be Able to: Compare the structure and function of arteries, arterioles, capillaries, and veins Describe the relationship between interstitial fluid, plasma, and lymph. Describe factors that contribute to venous return against gravity Define vasoconstriction and vasodilation Describe the three types of capillaries Explain the causes and risk factors of atherosclerosis. Explain how the lymph and lymphatic system relate to the blood and cardiovascular system. Describe the function of the lymphatic system.