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Transcript
Lecture Notes Chapter 17 Functional Anatomy of the Cardiovascular System Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 1 Gross Anatomy of the Heart Lies in mediastinum behind sternum Apex points to the left Point of maximal impact (PMI) The apical beat 5th Intercostal space at mid-clavicular line Causes of PMI shift • Left Sided Pneumothorax • Pg. 301 ConceptQuestion 17-1 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 2 Clinical Focus 17-1 32 y.o. man. Severe chest wall injury sustained in automobile accident. Conscious, anxious, c/o dyspnea and chest pain. Distending neck veins, tachycardia; systolic blood pressure of 90mmHg. Read the discussion (pg. 304) 1. The patient exhibits signs of ________________ 2. What is this disease? 3. Cause of distended neck veins? 4. Cause of increased HR? 5. Cause of low systolic pressure? 3 Pericardium Loose-fitting membranous sac Parietal vs. visceral pericardium (epicardium) Pg. 302 4 Parietal = outter sac Visceral (epicardium) = inner The fluid in between = pericardial fluid… Acts as lubrication allowing for smoother, frictionless movement as the heart beats. 5 Anatomy of the Heart Heart wall Epicardium, Myocardium, Endocardium Myocardium = Heart chambers and valves 2 atria and 2 ventricles RA receives deoxygenated blood from superior vena cava, inferior vena cava LA receives oxygenated blood from pulmonary veins • Greater muscle mass than the right ventricle Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 6 Anatomy of the Heart Fig. 17-3 Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 7 Anatomy of the Heart Heart chambers and valves Atrial-ventricular valves • Tricuspid = Right or Left side? ConceptQuestion 17-2 • Mitral = Right or Left side? • PURPOSE = prevent back flow of blood during ventricle contractions Ventricular outflow pg 302 • Right Ventricle Pumps through _________________ • Left Ventricle Pumps through __________________ • Prevents backflow of blood into the ventricles during ventricle relaxation 8 Clinical Focus 17-3 Mitral Valve Stenosis Person with Severe Mitral Valve Stenosis requires oxygen and shows signs of pulmonary edema. What is Pulmonary Edema? What is the connection of a cardiac problem leading to a pulmonary problem? 9 Clinical Focus 17-2 Ventricular Septal Defect (VSD) What is it? Mixing of blood from the two chambers Treatment? If patient is symptomatic (SOB), it will need surgical correction. 10 Coronary Circulation Though the heart pumps blood, it also receives oxygenated blood to sustain itself Coronary arteries Left and right coronaries • 1. Right coronary is the dominant blood supplier • 2. Originate immediately above aortic semilunar valve • 3. “The heart relies almost exclusively on the two main coronary arteries.” pg 305 In the heart, there is a lack of collateral circulation if… 1. If blood flow is blocked = ischemia (tissue hypoxia) and central chest pain (angina pectoris) 2. Myocardial infarction (MI) = heart muscle tissue death MONA – Morphine, Oxygen, Nitroglycerin(vasodilator), Asprin (prevent blood clot) 11 Angina Pectoris pg 306 Aka Chest Pain Caused by: Coronary artery disease The pain is often felt beneath the sternum, in the left arm, and in the neck “About 35% of all deaths in the United States are caused by coronary artery disease” (CAD) pg. 306 12 Coronary Circulation Coronary veins pg 307 Flow parallel to arteries Empty into right atrium (coronary sinus) Oxygen requirement and blood flow O2 extraction ≈70% (compare to 25% whole body) during exercise = coronary flow O2 need governs coronary blood flow Tachycardia is a response by the heart that it needs more oxygen During exercise, because the heart can’t extract more oxygen from the supply it’s getting… It needs to increase the blood flow by increasing the heart rate and get oxygen more quickly. If you give the patient oxygen, the heart rate will come back down. Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 13 Cardiac Conduction System pg 309 Specialized cardiac muscle tissue (not neurons) Atria contract at last second (“atrial kick”) to complete ventricular filling Conduction Sinoatrial node (SA node) – Initiates Electrical Impulses. Travel down to the AV Node. Atrioventricular node (AV node) - Triggers initial contraction of ventricles. Trigger travels down the AV bundle. AV bundle aka “bundle of His”. The AV Bundle triggers down the right and left bundle branches. Bundle branches terminate into the Purkinje fibers Purkinje fibers carry the electrical signal to the ventricles (apex of the heart). Ventricles receive signal and contract. 14 Systole vs. Diastole Diastole Ventricle is relaxed and fills with blood Systole Ventricle contracts and ejects blood Copyright © 2007, 1998 by Mosby, Inc., an affiliate of Elsevier Inc. 15 Example In the _____________ phase, the mitral valve and tricuspid valve is open, but the semilunar valves remain closed. A. Aortic B. Diastolic C. Systolic D. Anacrotic 16 Example In the ______________ phase, the mitral valve and tricuspid valve remain closed, but the semilunar valves open. A. Aortic B. Diastolic C. Systolic D. Anacrotic 17 Cardiac Conduction System Time “Stalls” for Time Fig. 17-10 Total Time From Electrical Signal To Ventricular Contraction = 18 Cardiac Cycle Cardiac Cycle refers to a complete pumping cycle Ventricular filling PRELOAD Contraction (systole) and relaxation (diastole) Beginning of Systole to the end of diastole = 0.8 seconds 80% passive + 20% atrial “kick” 80% is blood flowing from atria into ventricle At the last moment, the atria kicks 20% more blood into the ventricle to get the ventricle ready to pump Ventricular emptying (contraction) AFTERLOAD Closure of the AV valves (1st heart sound) Isovolumetric contraction (all valves closed) Resistance to ejection = afterload pg 316 19 Volume of blood during cardiac cycle Ventricular filling PRELOAD Ventricular emptying (contraction) AFTER LOAD 120 mL of blood total in this phase “End-Diastolic” Volume Normal amount of blood that is ejected = Stroke volume = 70 mL How much is left in the ventricle? • 50mL • = “End-Systolic” Volume (Not the same as stroke volume) Cycle repeats itself and the ventricle is filled back up to 120mL in the preload phase. If 70mL out of 120mL is ejected, what’s the percentage of ejected blood? 20 … this is known as… EJECTION FRACTION Ejection fraction… Percentage is 58 or about 60%. (Normal ≈ 60%.) A low ejection fraction = Indicates = Less than 50% indicates poor contractility and pumping failure On the flip side, during exercise, the ejection fraction may increase up to 90% pg 316 21 From Previous Slide Ventricular emptying (contraction) AFTER LOAD Normal amount of blood that is ejected = Stroke volume = 70 mL How much is left in the ventricle? • 50mL • = “End-Systolic” Volume (Not the same as stroke volume) Two ways to calculate Stroke Volume 1. Cardiac Output(mL) / HR 2. Preload – Afterload 22 Determining Stroke Volume Cardiac Output(mL) / HR Example: C.O = 5L/min HR = 80/min S.V. = ____ mL Example: C.O. = 3 L/min HR = 120/min S.V. = ______ mL 23 Determining Stroke Volume The following information is obtained: HR 120/min Preload volume 120mL Afterload Volume 80mL B/P 109/75mmHg What is the stroke volume? A. 210mL B. 90mL C. 50mL D. 40mL Preload – Afterload (D) 24 Summary Which of the following is known as enddiastolic volume? A. Afterload B. Stroke Volume C. Preload D. Diastole C. Preload Go back 5 slides ago 25 Regulation of Pumping Activity Normally, the blood that comes in (Right Atrium) is pumped out (Left Ventricle) at the same rate The heart has the ability to adapt to inflow changes “Frank-Starling Mechanism” The heart may lose its ability to adapt is the left ventricle’s muscle has been over stretched Left Ventricle Fails Blood backs up Congestive Heart Failure pg 314 26