Chapter 14 The Heart and Heart Disease
Circulation and the Heart • Circulation • Continuous one-way circuit of the blood vessels • Propelled by heart
Location of the Heart • Between the lungs • Left of the midline of the body • In mediastinum • Apex pointed toward left
Structure of the Heart • Three tissue layers • Endocardium lines heart’s interior • Myocardium is thickest layer • Epicardium is thin outermost layer
The Pericardium • The sac that encloses the heart • Fibrous pericardium holds heart in place • Serous membrane • Parietal layer • Pericardial cavity • Visceral layer (epicardium)
Layers of the heart wall and pericardium. The serous pericardium covers the heart and lines the fibrous pericardium.ZOOMING IN • Which layer of the heart wall is the thickest?
Checkpoint 14-1: What are the names of the innermost, middle, and outermost layers of the heart? Checkpoint 14-2: What is the name of the sac that encloses the heart?
Special Features of the Myocardium • Cardiac muscles • Are lightly striated (striped) • Have single nucleus cells • Are controlled involuntarily • Have intercalated disks • Have branching muscle fibers
Divisions of the Heart • Double pump • Right side pumps blood low in oxygen to the lungs • Pulmonary circuit • Left side pumps oxygenated blood to remainder of body • Systemic circuit
Four Chambers • Right atrium • Receives low-oxygen blood returning from body tissue through superior vena cava and inferior vena cava • Left atrium • Receives high-oxygen blood from lungs • Right ventricle • Pumps blood from right atrium to lungs • Left ventricle • Pumps oxygenated blood to body
The heart as a double pump. The right side of the heart pumps blood through the pulmonary circuit to the lungs to be oxygenated; the left side of the heart pumps blood through the systemic circuit to all other parts of the body. ZOOMING IN • What vessel carries blood into the systemic circuit?
The heart and great vessels. ZOOMING IN • Which heart chamber has the thickest wall?
Checkpoint 14-3: The heart is divided into four chambers. What is the upper receiving chamber on each side called? What is the lower pumping chamber called?
Four Valves • Atrioventricular valves • Entrance valves • Right atrioventricular (AV) valve (tricuspid valve) • Left atrioventricular (AV) valve (bicuspid valve) • Semilunar valves • Exit valves • Pulmonary valve • Aortic valve
Valves of the heart (superior view from anterior, atria removed). (A) When the heart is relaxed (diastole), the AV valves are open and blood flows freely from the atria to the ventricles. The pulmonary and aortic valves are closed. (B) When the ventricles contract, the AV valves close and blood pumped out of the ventricles opens the pulmonary and aortic valves.ZOOMING IN • How many cusps does the right AV valve have? The left?
Pathway of blood through the heart. Blood from the systemic circuit enters the right atrium (1) through the superior and inferior venae cavae, flows through the right AV (tricuspid) valve (2), and enters the right ventricle (3). The right ventricle pumps the blood through the pulmonary (semilunar) valve (4) into the pulmonary trunk, which divides to carry blood to the lungs in the pulmonary circuit. Blood returns from the lungs in the pulmonary veins, enters the left atrium (5), and flows through the left AV (mitral) valve (6) into the left ventricle (7). The left ventricle pumps the blood through the aortic (semilunar) valve (8) into the aorta, which carries blood into the systemic circuit.
Blood Supply to the Myocardium • Coronary circulation • Right coronary artery • Left coronary artery • Coronary sinus
Blood vessels that supply the myocardium. Coronary arteries and cardiac veins are shown. (A) Anterior view. (B) Posterior view.
Opening of coronary arteries in the aortic valve (anterior view). (A) When the left ventricle contracts, the aortic valve opens. The valve cusps prevent filling of the coronary arteries. (B) When the left ventricle relaxes, backflow of blood closes the aortic valve and the coronary arteries fill.
Checkpoint 14-5: The myocardium must have its own vascular system to supply it with blood. What name is given to this blood supply to the myocardium?
Function of the Heart • Left and right sides of heart work together in cardiac • cycle (heartbeat) • Systole (active phase, contraction) • Diastole (resting phase)
The cardiac cycle.ZOOMING IN • When the ventricles contract, what valves close? What valves open?
Cardiac Output • Calculating cardiac output • Cardiac output (CO) • Stroke volume (SV) • Heart rate (HR) • CO = HR 3 SV
Checkpoint 14-6: The cardiac cycle consists of an alternating pattern of contraction and relaxation. What name is given to the contraction phase? Checkpoint 14-7: Cardiac output is the amount of blood pumped by each ventricle in 1 minute. What two factors determine cardiac output?
The Heart’s Conduction System • Electrical energy stimulates heart muscle • Nodes • Sinoatrial (SA) node (pacemaker) • Atrioventricular (AV) node • Specialized fibers • Atrioventricular bundle (bundle of His) • Purkinje fibers (conduction myofibers) • Intercalated disks
Conduction system of the heart. The sinoatrial (SA) node, the atrioventricular (AV) node, and specialized fibers conduct the electrical energy that stimulates the heart muscle to contract. ZOOMING IN • What parts of the conduction system do the internodal pathways connect?
The Conduction Pathway • Sinus rhythm • Sinoatrial (SA) node • Atria • Atrioventricular (AV) node • Internodal pathways • Bundle of His • Bundle branches and Purkinje fibers • Ventricles
Checkpoint 14-8: The heartbeat is started by a small mass of tissue in the upper right atrium. This structure is commonly called the pacemaker, but what is its scientific name?
Control of the Heart Rate • Influences that allow heart to meet changing needs rapidly • Autonomic nervous system (ANS) • Sympathetic nervous system • Parasympathetic system • Cranial nerve X
Variations in Heart Rates • Bradycardia • Tachycardia • Sinus arrhythmia • Premature beat (extrasystole)
Heart Sounds • Lubb • Dupp • Murmurs • Organic • Functional
Checkpoint 14-9: What system exerts the main influence on the rate and strength of heart circulation? Checkpoint 14-10: What is a heart murmur?
Heart Disease Most common cause of death in industrialized countries is heart and circulatory system disease
Classifications of Heart Disease • Anatomical classification • Endocarditis • Myocarditis • Pericarditis • Causative factors classification • Congenital heart disease • Rheumatic heart disease • Coronary artery disease • Heart failure
Congenital Heart Disease • Congenital heart disease often results from fetal • development defects • Atrial septal defect • Patent (open) ductus arteriosus • Ventricular septal defect • Coarctation of the aorta • Tetralogy of Fallot
Rheumatic Heart Disease • Streptococci release toxins during infection • Antibodies that combat toxin also attack heart valves • Heart valves become inflamed • Valve cusps thicken and harden • Pulmonary congestion occurs
Coronary Artery Disease • Coronary arteries can degenerate • Myocardial infarction • Angina pectoris • Abnormalities of heart rhythm • Treatment of heart attacks
Checkpoint 14-13: Narrowing or blockage of the vessels that supply the heart muscle causes coronary artery disease. What degenerative process commonly causes narrowing of these vessels?
Heart Failure • Heart is unable to pump sufficient blood • Heart chambers enlarge • Blood backs up into lungs • Ventricular muscles have decreased ability • Fluid accumulates in lungs, liver, abdomen, legs
The Heart in the Elderly • How the heart can age • Heart shrinks • Decreased contraction strength • Valves become less flexible • Murmur develops • Cardiac output decreases • Abnormal rhythms • Heart block
Prevention of Heart Disease • Risk factors that cannot be modified • Age • Gender • Heredity • Body type • Risk factors that can be modified • Smoking • Physical inactivity • Weight • Diet • Blood pressure • Diabetes, gout
Heart Studies • Stethoscope • Electrocardiograph (ECG or EKG) • Electrodes • Catheterization • Fluoroscope • Echocardiography (ultrasound cardiography) • Oscilloscope
Treatment of Heart Disease • Medical approaches • Surgical approaches • Combined approaches
Medications • Digitalis • Nitroglycerin • Beta-adrenergic blocking agents (beta-blockers) • Antiarrhythmic agents • Slow calcium-channel blockers • Anticoagulants • Aspirin
Correction of Arrhythmias • Artificial pacemaker • Set rate • Only when heart skips beat • Adjustable pacing rate • Implantable cardioverter-defibrillator (ICD)
Heart Surgery • Coronary artery bypass graft (CSBG) • Angioplasty • Valve replacement • Surgical transplantation of heart or heart and lungs • Artificial heart