Copyright © 2004 Lippincott Williams & Wilkins Chapter 13 The Heart

Copyright © 2004 Lippincott Williams & Wilkins Circulation and the Heart Circulation –Continuous one-way circuit of the blood in vessels –Propelled by heart

Copyright © 2004 Lippincott Williams & Wilkins Location of the Heart Between the lungs Left of the midline of the body In mediastinum Apex pointed toward left

Copyright © 2004 Lippincott Williams & Wilkins The heart in position in the thorax (anterior view) ZOOMING IN Why is the left lung smaller than the right lung? Because most of the heart is on the left side

Copyright © 2004 Lippincott Williams & Wilkins Structure of the Heart Three tissue layers –Endocardium lines heart’s interior –Myocardium is thickest layer –Epicardium is thin outermost layer

Copyright © 2004 Lippincott Williams & Wilkins The Pericardium The sac that encloses the heart –Fibrous pericardium holds heart in place –Serous pericardium Two layers –Parietal layer –Visceral layer (epicardium) Pericardial cavity between layers

Copyright © 2004 Lippincott Williams & Wilkins Layers of the heart wall and pericardium ZOOMING IN Which layer of the heart wall is the thickest?Left ventricle

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 13-1: What are the names of the innermost, middle, and outermost layers of the heart? –Endocardium, myocardium, epicardium Checkpoint 13-2: What is the name of the sac that encloses the heart? –Pericardium

Copyright © 2004 Lippincott Williams & Wilkins Special Features of the Myocardium Cardiac muscle –Lightly striated (striped) –Cells have single nucleus –Intercalated disks between cells –Muscle fibers branch –Controlled involuntarily

Copyright © 2004 Lippincott Williams & Wilkins Cardiac muscle tissue viewed under the microscope (x540).

Copyright © 2004 Lippincott Williams & Wilkins 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

Copyright © 2004 Lippincott Williams & Wilkins Four Chambers Right atrium –Receives deoxygenated blood returning from body tissue through superior vena cava and inferior vena cava Left atrium –Receives oxygenated blood from lungs Right ventricle –Pumps blood from right atrium to lungs Left ventricle –Pumps oxygenated blood to rest of body

Copyright © 2004 Lippincott Williams & Wilkins The heart as a double pump. ZOOMING IN What vessel carries Blood into the systemic circuit? The aorta

Copyright © 2004 Lippincott Williams & Wilkins The heart and great vessels ZOOMING IN Which heart chamber has the thickest wall? The left ventricle

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 13-3: The heart is divided into four chambers. What is the upper receiving chamber on each side called? –The right and left atrium What is the lower pumping chamber called? –The right and left ventricles

Copyright © 2004 Lippincott Williams & Wilkins Four Valves Atrioventricular valves –Entrance valves –Right atrioventricular (AV) valve (tricuspid valve) –Left atrioventricular (AV) valve (bicuspid [mitral] valve) Semilunar valves –Exit valves –Pulmonary valve –Aortic valve

Copyright © 2004 Lippincott Williams & Wilkins Valves of the heart (superior view from anterior, atria removed) ZOOMING IN How many cusps does the right AV valve have? The left? 3 (tricuspid) 2 (bicuspid)

Copyright © 2004 Lippincott Williams & Wilkins Pathway of blood through the heart

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 13-4: What is the purpose of valves in the heart? –To keep blood flowing in the right direction.

Copyright © 2004 Lippincott Williams & Wilkins Blood Supply to the Myocardium Coronary circulation –Right coronary artery –Left coronary artery –Cardiac veins –Coronary sinus

Copyright © 2004 Lippincott Williams & Wilkins Blood vessels that supply the myocardium

Copyright © 2004 Lippincott Williams & Wilkins Opening of coronary arteries in the aortic valve (anterior view)

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 13-5: The myocardium must have its own vascular system to supply it with blood. What name is given to this blood supply to the myocardium? –Coronary circulation

Copyright © 2004 Lippincott Williams & Wilkins Function of the Heart Left and right sides of heart work together in cardiac cycle (heartbeat) –Systole (active phase, contraction) –Diastole (resting phase)

Copyright © 2004 Lippincott Williams & Wilkins The cardiac cycle ZOOMING IN When the ventricles contract, what valves close? What valves open? AV valves The aortic valve and the pulmonary valve

Copyright © 2004 Lippincott Williams & Wilkins Cardiac Output Calculating cardiac output (CO) –Stroke volume (SV) –Heart rate (HR) CO = HR x SV

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 13-6: The cardiac cycle consists of an alternating pattern of contraction and relaxation. What name is given to the contraction phase? –Systole Checkpoint 13-7: Cardiac output is the amount of blood pumped by each ventricle in 1 minute. What two factors determine cardiac output? –Heart rate and stroke volume

Copyright © 2004 Lippincott Williams & Wilkins 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)

Copyright © 2004 Lippincott Williams & Wilkins The Conduction Pathway Sinus rhythm (normal heart rhythm) –Sinoatrial (SA) node Generates impulse –Atria Impulse travels through atria to – Internodal pathways Connect SA and AV nodes –Atrioventricular (AV) node Conducts impulse to ventricles and to the –Bundle of His And throughout the ventricular walls by the –Bundle branches and –Purkinje fibers

Copyright © 2004 Lippincott Williams & Wilkins Conduction system of the heart. ZOOMING IN What parts of the conduction system do the internodal pathways connect? The sinoatrial node and the atrioventricular node

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 13-8: 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? –Sinoatrial node

Copyright © 2004 Lippincott Williams & Wilkins Control of the Heart Rate Influences that allow heart to meet changing needs rapidly Autonomic nervous system (ANS) –Sympathetic nervous system Increases heart rate –Parasympathetic system Decreases heart rate Cranial nerve X (vagus)

Copyright © 2004 Lippincott Williams & Wilkins Autonomic nervous system regulation of the heart. ZOOMING IN what parts of the conduction system does the autonomic nervous system affect? The AV and SA nodes and myocardial fibers

Copyright © 2004 Lippincott Williams & Wilkins Variations in Heart Rates Bradycardia –Slow heart rate (below 60 beats/minute) Tachycardia –Rapid heart rate (greater than 100 beats/minute) Sinus arrhythmia –Changes in heart rate caused by breathing (normal) Premature beat (extrasystole) –Beat that comes before the expected normal beat

Copyright © 2004 Lippincott Williams & Wilkins Heart Sounds First heart sound (lubb) Second heart sound (dupp) Murmurs (abnormal heart sound) –Organic Caused by structural changes in the heart or vessels –Functional Normal sounds made by the heart working

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 13-9: What system exerts the main influence on the rate and strength of heart circulation? –The autonomic nervous system Checkpoint 13-10: What is a heart murmur? –An abnormal heart sound

Copyright © 2004 Lippincott Williams & Wilkins 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 Temporary failure of the conduction system

Copyright © 2004 Lippincott Williams & Wilkins Maintaining Heart Health 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

Copyright © 2004 Lippincott Williams & Wilkins Heart Studies Stethoscope Electrocardiograph (ECG or EKG) –Electrodes on the skin pick up the electrical activity of the heart and record it as waves Catheterization –A small catheter is placed in the great vessels of the heart to study the blood flow or blocked coronary arteries Echocardiography (ultrasound cardiography)

Copyright © 2004 Lippincott Williams & Wilkins Normal ECG Tracing ZOOMING IN What is the length of the cardiac cycle shown in the diagram? 0.8 sec

Copyright © 2004 Lippincott Williams & Wilkins Checkpoint 13-11: What do ECG and EKG stand for? –Electrocardiogram