Cardiovascular System PDF

Cardiovascular System Marie A. Román Martínez, PhD Department of Biology Office hours: by appointment Email: [email protected] Copyright-This presentation is intended for educational purpose only. No part of this presentation may be reproduced or transmitted in any form without written permission....

Cardiovascular System Marie A. Román Martínez, PhD Department of Biology Office hours: by appointment Email: [email protected] Copyright-This presentation is intended for educational purpose only. No part of this presentation may be reproduced or transmitted in any form without written permission. Objectives 1. Identify the protective coverings of the heart. 2. Describe the parts of the heart and their functions. 3. Trace the flow of blood through the heart. 4. Describe the blood supply to the heart. 5. Describe the events of the cardiac cycle. 6. Describe the sounds of the heartbeat. 7. Describe the parts of the conducting system of the heart and their functions. 8. Explain how the heart rate and contraction strength are regulated. 9. Describe the structure and function of arteries, arterioles, capillaries, venules, and veins. 10. Describe how materials are exchanged between capillary blood and interstitial fluid. 11. Describe the mechanism of blood circulation. 13. Describe how blood pressure is regulated. 14. Compare the systemic and pulmonary circuits. 15. Identify the major systemic arteries and the organs or body regions that they supply. 16. Identify the major systemic veins and the organs or body regions that they drain. 2 Introduction Heart and blood vessels form the cardiovascular system. Heart pumps blood. Blood vessels colored blue carry deoxygenated (oxygen-poor) blood. Blood vessels colored red carry oxygenated (oxygen-rich) blood. Arteries carry blood away from the heart to capillaries→ where materials are exchanged with interstitial fluid. Veins carry blood from capillaries to heart. 3 Location of the Heart Four chambered muscular pump. Lies between the lungs, above the diaphragm. The apex is the lower pointed end that extends to the left side. Broad base is the upper portion that is attached to large blood vessels. The heart is about the size of a closed fist. 4 Protective Coverings of the Heart Pericardium Loosely fitting sac that separates the heart from surrounding tissue. Allows space for the heart to expand and contract as it pumps blood. Consists of two membranes: Outer fibrous pericardium Inner parietal layer of serous pericardium 5 Protective Coverings of the Heart Pericardium Fibrous pericardium Tough, unyielding membrane. Parietal layer of serous pericardium Delicate membrane lining inner surface of fibrous pericardium. Folds back at the base to form the epicardium. Visceral layer of serous pericardium (epicardium) Thin membrane that tightly adheres to surface of the heart. Pericardial cavity Space between the parietal layer and visceral layer of serous pericardium. Filled with pericardial fluid→ reduces friction between the two layers when the heart contracts and expands. 6 The Heart Wall The heart wall consists of three layers: 1. Myocardium: Thick layer of cardiac muscle tissue. Provides force for contraction. 2. Epicardium: Outer layer. Contains blood vessels that nourish the heart. 3. Endocardium: Inner layer. Continuous with the inner lining of the blood vessels attached to heart. 7 Heart Chambers Two atria Upper chambers Receive blood from veins Two ventricles Lower chambers Pump blood into arteries Interatrial septum Separates the atria Interventricular septum Separates the ventricles 8 Posterior View of the Heart Image obtained from Figure 19.5 from Saladin Anatomy & Physiology 9th edition 9 Image obtained from Figure 19.7 from Saladin Anatomy & Physiology 9th edition Heart Chambers The heart is a double pump. Right pump→ right atrium and right ventricle. Left pump→ left atrium and left ventricle. Ventricles are much thicker→ creates enough force to pump blood up and out of the heart. The left ventricle is thicker→it must pump blood throughout the entire body, except the lungs. The right ventricle pumps blood only to the lungs. Blood movement from atria to ventricles is mostly passive. 10 Heart Valves Blood flows in one direction through the heart due to valves. The two types of heart valves are the atrioventricular valves and semilunar valves. Atrioventricular valves (AV valves) Allow flow from atria to ventricles Prevents backflow when ventricles contract Tricuspid valve (right atrioventricular valve) Between right atrium and the right ventricle. Three cusps or flaps of tissue. Mitral valve (left atrioventricular valve) Between left atrium and left ventricle. Two cusps. 11 Heart Valves AV valve structure Originate from the dense irregular connective tissue. Provides valve support. Serves as electrical insulation between atria and ventricles. Enables the atria and ventricles to contract independently. Tendinous cords extend from valve cusps to papillary muscles in ventricle walls. Thin strands of dense regular connective tissue. Prevent inversion of cusps when ventricles contract. 12 Image obtained from Figure 19.8 from Saladin Anatomy & Physiology 9th edition Heart Valves Semilunar valves Located at bases of large arteries that carry blood from the ventricles. Three pocket-like cusps. Allow blood to flow from ventricles into the arteries when ventricles contract. Prevent backflow of blood from the arteries into the ventricles when ventricles relax. Semilunar valves Pulmonary valve Between right ventricle and pulmonary trunk. Controls the opening from the right ventricle into the pulmonary trunk. Aortic valve Between left ventricle and aorta. Controls the opening from the left ventricle into the aorta. 13 14 Flow of Blood Through the Heart The right atrium receives deoxygenated blood from all parts of the body, except the lungs via three veins: Superior vena cava→ returns blood from the head, neck, shoulders, upper limbs, and thoracic and lumbar regions. Inferior vena cava→ returns blood from lower trunk and lower limbs. Coronary sinus→ drains deoxygenated blood from cardiac striated muscle. Simultaneously the left atrium receives oxygenated blood returning to the heart from the lungs via the pulmonary veins. 15 Flow of Blood Through the Heart After blood has flowed from the atria into their respective ventricles, the ventricles contract. The right ventricle pumps deoxygenated blood into the pulmonary trunk. Left pulmonary arteries Right pulmonary arteries Carry blood to the lungs The left ventricle pumps oxygenated blood into the aorta. Branches from the aorta carry blood to all parts of the body except the lungs. 16 Flow of Blood Through the Heart Two basic circuits of blood flow: 1. Pulmonary circuit Carries deoxygenated blood from right ventricle to the lungs. Returns oxygenated blood from lungs to the left atrium. 2. Systemic Circuit Carries oxygenated blood from the left ventricle to all parts of the body (except the lungs). Returns deoxygenated blood from the body (except the lungs) to the right atrium. 17 Blood Flow Through the Heart 18 Systemic vs. Pulmonary Circulation https://anatomy.mheducation.com/html/apr.html?animal=human&id=2 093 19 Blood Supply to the Heart The heart requires a constant supply of blood to nourish its own tissues. Left and right coronary arteries: Arise from the aorta just above the aortic valve. Supply myocardium with oxygenated blood. Blockage may result in a heart attack. Cardiac veins: Lie next to coronary arteries. Return deoxygenated blood to the coronary sinus, which drains into the right atrium. Image obtained from Figure 19.10 from Saladin Anatomy & Physiology 9th edition 20 Cardiac Cycle Cardiac cycle is the sequence of events that occur during heartbeat. Systole: Contraction phase. Increases blood pressure within a chamber. Diastole: Relaxation phase. Decreases blood pressure within a chamber. When ventricle contract, atria relax. When atria contract, ventricles relax. 21 Steps of Cardiac Cycle When atria and ventricles are relaxed, between beats, blood flows from large veins into the atria, then passively into ventricles. AV valves open. Semilunar valves close. Next, atrial systole forces more blood into relaxed ventricles, so that they are filled. 22 Steps of Cardiac Cycle Next, ventricular systole increases blood pressure in ventricles. Closes AV valves and opens semilunar valves. Blood moves from ventricles and into arteries. Ventricular diastole then follows. Decrease in ventricular pressure allows AV valves to open and semilunar valves to close (because of the greater blood pressure within the arteries). Cycle repeats. 23 24 Blood Flow through the heart https://anatomy.mheducation.com/html/apr.html?animal=human& 25 Heart Sounds Usually described as lub-dup (pause) lub-dup and so forth. These sound are produced by the closing of the heart valves: Lub (S1): closing of AV valves at the start of ventricular systole. Dub (S2): closing of semilunar valves at the start of ventricular diastole. If any of the heart valves are defective and do not close properly, an additional sound known as heart murmur, may be heard. 26 Conducting System of the Heart The conducting system of the heart consists of specialized cardiac muscle tissue. Spontaneously form action potentials. Transmits action potentials to myocardium to initiate contraction. Components: Bachmann’s bundle Sinoatrial (SA) node Atrioventricular (AV) node Bachmann’s bundle Atrioventricular (AV) bundle Right and left bundle branches Subendocardial conducting network 27 Conducting System of the Heart Sinoatrial node: Pacemaker of the heart→ rhythmically forms action potentials to initiate each heartbeat. Action potentials are transmitted to the myocardium of the atria cause simultaneous contraction of atria. Bachmann’s bundle Forcing blood into the ventricles. Atrioventricular node: Receives action potentials from SA node. Delay in passing action potentials through node. Allows time for ventricles to fill with blood. Passes action potentials to the AV bundle. 28 Conducting System of the Heart AV bundle: Divides into left and right bundle branches. Bachmann's Bundle Carry action potentials down the interventricular septum and upward to the lateral ventricle walls. Forms the subendocardial conducting network. Ventricular fibers arises from the bundle branches. Carry action potentials to myocardium of ventricles. Stimulate ventricular contraction. Contraction occurs from the apex upward so that blood is forced into the pulmonary trunk and aorta. 29 Electrocardiogram (ECG or EKG) Recording of the electrical current generated by the conducting system of the heart that may be detected by electrodes placed on the body surface. Performed using an electrocardiograph. Provides important information in the diagnosis of heart disease and abnormalities. An ECG showing one cardiac cycle An ECG showing five cardiac cycles 30 Electrocardiogram (ECG or EKG) Possess three distinct waves. P wave Atrial depolarization QRS complex Ventricular depolarization Greater size due to the greater muscle mass of the ventricles. T wave Ventricular repolarization Repolarization of the atria is not detected because it is masked by the stronger QRS complex. 31 Cardiac Cycle 32 Cardiac Output (CO) Cardiac output is the volume of blood pumped from each ventricle per minute. Determined by: Stroke volume (SV): volume of blood pumped out of each ventricle per heartbeat. Heart rate (HR): number of heartbeats per minute. CO = SV x HR On average at rest: Stroke volume =70 ml/beat Heart rate= 72 beats/min Cardiac output= 4 to 6 liters/min Cardiac output increase with exercise because both stroke volume and heart rate increase. 33 Cardiac Output (CO) Heart function is regulated by intrinsic and extrinsic factors. For example, venous return: The amount of blood returning to the heart during diastole. Intrinsic factor affecting stroke volume. ↑venous return, ↑stroke volume, ↑CO. HR is primarily regulated extrinsically through the autonomic division, although hormones and certain ions also affect it. 34 Autonomic Regulation Heart rate regulation is primarily under control of the cardiac control center in the medulla oblongata of the brain. Cardiac control center receives input from: Baroreceptors in aortic arch and carotid sinuses of the internal carotid arteries. Stimulated by changes in vessel wall stretching due to blood pressure changes. Chemoreceptors in aortic arch and carotid bodies. Stimulated by;↓blood pH, ↑ blood CO2, ↓ blood O2. The cardiac control center is also affected by emotions created by limbic system. 35 Autonomic Regulation The cardiac control center consists of both sympathetic and parasympathetic components. Sympathetic neurons ↑heart rate and contraction force. Axons innervate SA node (also AV node and parts of myocardium). Secrete norepinephrine: ↑heart rate ↑ force of myocardial contraction. Physical and emotional stresses stimulate the sympathetic part. 36 Autonomic Regulation Parasympathetic neurons ↓heart rate. Axons innervate the SA and AV nodes. Secretes acetylcholine: Slows heart rate Stimulated by excessive blood pressure and emotional factors. ↑frequency of parasympathetic action potentials sent to the heart, the slower the heart rate. At rest, parasympathetic action potentials predominate. 37 Other Factors Affecting Heart Function Resting heart rate declines with age Heart rate in females slightly faster than males Good physical condition ↓heart rate Temperature ↑temperature, ↑ heart rate Sex Epinephrine ↑ heart rate and strength of heart contractions Physical condition Thyroxine Age ↑heart rate 38 Other Factors Affecting Heart Function Potassium Higher levels, ↓heart rate and force of contraction. Abnormally high levels can stop the heart. Lower levels can cause abnormal heart rhythms. Lethal injection→ dangerously high level of blood K+ causes the heart to stop contracting. Calcium Lower levels, ↓ heart rate and contractions strength. Higher levels, ↑ heart rate and contraction strength, in addition to prolonging contraction. 39