Heart & Heart Disease Chapter 14 PDF

Heart & Heart Disease Chapter 14  Learning Objectives Lesson 14.1: Anatomy and Blood Flow in the Heart 1. Discuss the location, size, and position of the heart in the thoracic cavity. 2. Identify and discuss the heart chambers, pericardium, heart valves, and major valve...

Heart & Heart Disease Chapter 14  Learning Objectives Lesson 14.1: Anatomy and Blood Flow in the Heart 1. Discuss the location, size, and position of the heart in the thoracic cavity. 2. Identify and discuss the heart chambers, pericardium, heart valves, and major valve disorders. 3. Discuss the typical heart sounds and identify common atypical heart sounds. 4. Trace blood through the heart, compare the functions of the heart chambers on the right and left sides, and explain how a myocardial infarction might occur. Location, Size, and Position of the Heart  Triangular organ located in mediastinum with two-thirds of the mass to the left of the body midline and one-third to the right; the apex is on the diaphragm  Shape and size of a closed fist The Heart  Location of the Heart  Heart lies between the sternum in front and the bodies of the thoracic vertebrae behind  Rhythmic compression of the heart between the sternum and vertebrae can maintain blood flow during cardiac arrest  If combined with artificial respiration procedure, it can be lifesaving Functional Anatomy of the Heart  Heart chambers  Two upper chambers are called atria (receiving chambers): Right and left atria  Two lower chambers called ventricles (discharging chambers): Right and left ventricles  Heart Chambers  Wall of each heart chamber is composed of cardiac muscle tissue called myocardium  Endocardium: Smooth lining of heart chambers  Inflammation of endocardium is called endocarditis  Inflamed endocardium can become rough and abrasive and thereby cause a thrombus  Pericardium and Pericarditis  Pericardium: Two-layered fibrous sac with a lubricated space between the two layers  Inner layer is called visceral pericardium or epicardium  Outer layer called parietal pericardium  Pericarditis: Inflammation of the pericardium  Cardiac tamponade: Compression of the heart caused by fluid building up between the visceral pericardium and parietal pericardium Internal View of the Heart  Heart Action (1 of 2)  Contraction of the heart is called systole  Relaxation of the heart is called diastole Heart Action (2 of 2)  Heart Valves  Valves keep blood flowing through the heart; prevent backflow  Atrioventricular (AV) valves  Tricuspid: At the opening of the right atrium into the ventricle  Bicuspid (mitral): At the opening of the left atrium into the ventricle  Semilunar (SL) Valves  Pulmonary semilunar: At the beginning of the pulmonary artery  Aortic semilunar: At the beginning of the aorta  Valve Conditions  Incompetent valves “leak,” allowing some blood to flow backward into the chamber from which it came  Stenosed valves are narrower than normal, reducing blood flow  Rheumatic heart disease: Cardiac damage resulting from a delayed inflammatory response to streptococcal infection  Mitral valve prolapse (MVP): Incompetence of mitral valve caused by its edges extending back into left atrium when left ventricle contracts  Mitral Valve Stenosis From Kumar V, Abbas AK, Fausto N: Robbins and Cotran pathologic basis of disease, ed 8, Philadelphia, 2010, Elsevier. Mitral Valve Prolapse (MVP)  Heart Sounds  Two distinct heart sounds in every heartbeat, or cycle—lub dup  First sound (lub) caused by the vibration and closure of AV valves during contraction of the ventricles  Second sound (dup) caused by the closure of the SL valves during relaxation of the ventricles  Heart murmurs: Abnormal heart sounds often caused by abnormal valves  Blood Flow Through the Heart  Heart acts as two separate pumps: The right atrium and ventricle perform different functions from the left atrium and ventricle Blood Flow Through the Cardiovascular System  Sequence of Blood Flow  Venous blood enters the right atrium through the superior and inferior venae cavae  Passes from the right atrium through the tricuspid valve to the right ventricle  From the right ventricle through the pulmonary semilunar (SL) valve to the pulmonary artery to the lungs  Blood from the lungs to the left atrium, passes through the bicuspid (mitral) valve to left ventricle  Blood in the left ventricle is pumped  Blood Supply to the Heart Muscle (1 of 2)  Blood, which supplies oxygen and nutrients to the myocardium of the heart, flows through the right and left coronary arteries  Blockage of blood flow through the coronary arteries can cause myocardial infarction (MI; heart attack) Blood Supply to the Heart Muscle (2 of 2)  Coronary Heart Disease (1 of 2)  Coronary thrombosis and coronary embolism involve a blood clot blocking some part of a coronary artery  Blood cannot flow through to the heart, and those cells start to die  Myocardial infarction (MI), or tissue death, occurs  Coronary Heart Disease (2 of 2)  Atherosclerosis: Type of “hardening of arteries” in which lipids build up on the inside wall of blood vessels; can partially or totally block coronary blood flow  Angina pectoris: Chest pain caused by inadequate oxygen to the heart  Coronary Bypass Surgery  Common treatment for patients with severely restricted coronary artery blood flow  Other veins or vessels are taken from the body and used to bypass blockages in the coronary arteries  Learning Objectives Lesson 14.2: Understanding the Cardiac Cycle, Electrical Conduction, Dysrhythmias, and Heart Failure 5. Explain the cardiac cycle. 6. List the anatomical components of the heart conduction system and discuss the features of the typical electrocardiogram. 7. Describe the major types of cardiac dysrhythmias. 8. Explain how heart rate and stroke volume affect cardiac output. 9. List and describe the possible causes of heart failure.  Cardiac Cycle  Heartbeat is regular and rhythmical— each complete beat called a cardiac cycle—average is about 72 beats per minute  Each cycle, about 0.8 seconds long, subdivided into systole (contraction phase) and diastole (relaxation phase) Conduction System of the Heart (1 of 2)  Normal structure and function  SA (sinoatrial) node, the pacemaker: Located in the wall of the right atrium near the opening of the superior vena cava  AV (atrioventricular) node: Located in the right atrium along the lower part of the interatrial septum  AV bundle (bundle of His): Located in the septum of the ventricle  Purkinje fibers (subendocardial fibers): Located in the walls of the ventricles Conduction System of the Heart (2 of 2)  Electrocardiography  Specialized conduction system structures generate and transmit the electrical impulses that result in contraction of the heart  These tiny electrical impulses traveling through the heart's conduction system can be picked up on the surface of the body and transformed into visible tracings by a machine called an electrocardiograph  The visible tracing of these electrical signals is called an electrocardiogram, or  ECG Deflections  Electrocardiography  The normal ECG has three deflections or waves P wave: Associated with depolarization of the atria QRS complex: Associated with depolarization of the ventricles T wave: Associated with repolarization of the ventricles Events Represented by the ECG (1 of 2) Events Represented by the ECG (2 of 2)  Cardiac Dysrhythmias  Abnormality of heart rhythm  Heart block: Conduction of impulses is blocked Complete heart block: Impaired AV node conduction, producing complete dissociation of P waves from QRS complexes Can be treated by implanting an artificial pacemaker Dysrhythmias  Types of Dysrhythmias  Bradycardia: Slow heart rate (less than 60 beats/min)  Tachycardia: Rapid heart rate (more than 100 beats/min)  Sinus dysrhythmia: Variation in heart rate during breathing cycle  Premature contraction (extrasystole): Contraction that occurs sooner than expected in a normal rhythm  Fibrillation: Cardiac muscle fibers are “out of step,” producing no effective pumping action  Fibrillation  Atrial fibrillation (AF or A-fib): Occurs in mitral stenosis, rheumatic heart disease, and infarction of atrial myocardium  Ventricular fibrillation (VF or V-fib): Life- threatening; occurs when a lack of ventricular pumping stops blood flow to vital tissues  Defibrillation: Can treat fibrillation by applying an electric shock to force cardiac fibers back into rhythm  AEDs and Atrial Ablation  Automatic external defibrillators (AEDs) are small, lightweight devices that detect heart rhythms and can produce a shock, if necessary  Atrial ablation is used to treat atrial fibrillation by destroying heart muscle in a specific location and eliminating the pathway of abnormal electrical signals  Cardiac Output (1 of 2)  Stroke volume is the volume of blood ejected from one ventricle with each beat  Cardiac output (CO) is amount of blood that one ventricle can pump each minute: Average is about 5 L per minute at rest  CO is determined by heart rate (HR) and stroke volume (SV)  HR (beats/min)×SV (volume/beat) = CO (volume/min) Cardiac Output (2 of 2)  Heart Rate (HR)  Autonomic nervous system (ANS) can alter the heart’s rhythm to increase or decrease HR  When blood CO levels rise with 2 exercise, HR rises to restore homeostasis of blood gases  Sudden drop in blood pressure can increase HR to restore normal blood flow  Stroke Volume (SV)  The volume of blood ejected by the ventricles is determined by the volume of blood returned to the heart by the veins, or venous return  The higher the venous return, the higher the SV  Strength of myocardial contraction also helps determine SV  Valve disorders, coronary artery blockage, and myocardial infarction (MI) can all decrease stroke volume and may decrease cardiac output  Heart Failure (1 of 2)  Heart failure: Inability to pump enough returned blood to sustain life; it can be caused by many different heart diseases  Right heart failure: Failure of the right side of the heart to pump blood, usually because the left side of the heart is not pumping effectively  Heart Failure (2 of 2)  Left heart failure (congestive heart failure, CHF): Inability of the left ventricle to pump effectively, resulting in congestion of the systemic and pulmonary circulations  Diseased hearts can be replaced by donated living hearts (transplants) or by artificial hearts (implants), although both procedures have yet to be perfected Cor Pulmonale Heart Transplant Courtesy Patricia Kane, Indiana University Medical School. Questions?