Memmler’s The Human Body in Health and Disease 11th edition Chapter 14 The Heart and Heart Disease “Cheerfulness is the best promoter of health and is as friendly to the mind as to the body.” Joseph Addison

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; the heart muscle 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 Layers of the heart wall and pericardium. The serous pericardium covers the heart and lines the fibrous pericardium. Which layer of the heart wall is the thickest?

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 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. What vessel carries blood into the systemic circuit?

The heart and great vessels. Which heart chamber has the thickest wall?

Question: Which chamber of the heart receives oxygenated blood coming in from the lungs in the pulmonary veins? a. right atrium b. left ventricle c. left atrium

Answer: c. left atrium (upper left chamber)

Four Valves in Relation to Ventricles 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) 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 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) 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.

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 X SV

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) Bundle branches Purkinje fibers (conduction myofibers) Intercalated disks

Conduction system of the heart 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. 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

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 Lub Dup Murmurs Organic Functional

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 Creatine kinase released upon any muscle damage. Tests for certain forms of CK indicate whether an MI occurred. Angina pectoris Abnormalities of heart rhythm Treatment of heart attacks

Heart Failure Heart is unable to pump sufficient blood for the body’s needs 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 Anti-platelet aggregates Plavix, Aspirin Anticoagulants Heparin, Lovenox, Coumadin

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 (CABG) Angioplasty Valve replacement Surgical transplantation of heart or heart and lungs Artificial heart