PowerPoint ® Lecture Slides prepared by Leslie Hendon University of Alabama, Birmingham C H A P T E R Copyright © 2011 Pearson Education, Inc. Part 1 19 The Heart

Copyright © 2011 Pearson Education, Inc. The Heart—typically weighs 250–350 grams A muscular double pump Pulmonary circuit—takes blood to and from the lungs Systemic circuit—vessels transport blood to and from body tissues Atria—receive blood from the pulmonary and systemic circuits Ventricles—the pumping chambers of the heart

Copyright © 2011 Pearson Education, Inc. The Pulmonary and Systemic Circuits Figure 19.1 Oxygen-rich, CO 2 -poor blood Oxygen-poor, CO 2 -rich blood Capillary beds of lungs where gas exchange occurs Capillary beds of all body tissues where gas exchange occurs Pulmonary veins Pulmonary arteries Pulmonary Circuit Systemic Circuit Aorta and branches Left atrium Heart Left ventricle Right atrium Right ventricle Venae cavae

Copyright © 2011 Pearson Education, Inc. (c) Superior vena cava Left lung Aorta Parietal pleura (cut) Pericardium (cut) Pulmonary trunk Diaphragm Apex of heart Location of the Heart in the Thorax Figure 19.2 Heart Posterior Right lung (b) Mediastinum Pericardium (cut) Fat in epicardium Rib 5 Left lung Aorta Mediastinum Apex of heart (d) Right auricle of right atrium Superior vena cava Right ventricle Diaphragm (a) Rib 2 Midsternal line

Copyright © 2011 Pearson Education, Inc. Four “Corners” of the Heart Superior right At costal cartilage of third rib and sternum Inferior right At costal cartilage of sixth rib lateral to the sternum Superior left At costal cartilage of second rib lateral to the sternum Inferior left Lies in the fifth intercostal space at the midclavicular line

Copyright © 2011 Pearson Education, Inc. Structure of the Heart—Coverings Pericardium—two primary layers Fibrous pericardium Strong layer of dense connective tissue Serous pericardium Formed from two layers Parietal layer of the serous pericardium Visceral layer of the serous pericardium

Copyright © 2011 Pearson Education, Inc. Layers of the Pericardium and of the Heart Wall Figure 19.3 Fibrous pericardium Parietal layer of serous pericardium Pericardial cavity Epicardium (visceral layer of serous pericardium) Myocardium Endocardium Pulmonary trunk Heart chamber Heart wall Pericardium Myocardium

Copyright © 2011 Pearson Education, Inc. Structure of the Heart—Layers of the Heart Wall Epicardium Visceral layer of the serous pericardium Myocardium Consists of cardiac muscle Muscle arranged in circular and spiral patterns Endocardium Endothelium resting on a layer of connective tissue Lines the internal walls of the heart

Copyright © 2011 Pearson Education, Inc. Circular and Spiral Arrangements of Cardiac Muscle Bundles Figure 19.4 Cardiac muscle bundles

Copyright © 2011 Pearson Education, Inc. Gross Anatomy of the Heart Figure 19.5b Left common carotid artery Left subclavian artery Aortic arch Ligamentum arteriosum Left pulmonary artery Left pulmonary veins Auricle of left atrium Circumflex artery Left coronary artery (in coronary sulcus) Left ventricle Great cardiac vein Anterior interventricular artery (in anterior interventricular sulcus) Apex (b) Anterior view Brachiocephalic trunk Superior vena cava Right pulmonary artery Ascending aorta Pulmonary trunk Right pulmonary veins Right atrium Right coronary artery (in coronary sulcus) Anterior cardiac vein Right ventricle Right marginal artery Small cardiac vein Inferior vena cava

Copyright © 2011 Pearson Education, Inc. Heart Chambers Figure 19.5e Aorta Left pulmonary artery Left atrium Left pulmonary veins Mitral (bicuspid) valve Aortic valve Pulmonary valve Left ventricle Papillary muscle Interventricular septum Epicardium Myocardium Endocardium (e) Frontal section Superior vena cava Right pulmonary artery Pulmonary trunk Right atrium Right pulmonary veins Fossa ovalis Pectinate muscles Tricuspid valve Right ventricle Chordae tendineae Trabeculae carneae Inferior vena cava

Copyright © 2011 Pearson Education, Inc. Heart Valves—Valve Structure Each valve composed of Endocardium with connective tissue core Atrioventricular (AV) valves Between atria and ventricles Aortic and pulmonary valves At junction of ventricles and great arteries

Copyright © 2011 Pearson Education, Inc. Fibrous Skeleton Surrounds all four valves Composed of dense connective tissue Functions Anchors valve cusps Prevents overdilation of valve openings Main point of insertion for cardiac muscle Blocks direct spread of electrical impulses

Copyright © 2011 Pearson Education, Inc. Heart Valves—Valve Structure Figure 19.6a Pulmonary valve Aortic valve Area of cutaway Mitral valve Tricuspid valve Myocardium Tricuspid (right atrioventricular) valve (a) Mitral (left atrioventricular) valve Aortic valve Pulmonary valve Fibrous skeleton Anterior

Copyright © 2011 Pearson Education, Inc. Function of the Atrioventricular Valves Figure 19.7a Blood returning to the heart fills atria, putting pressure against atrioventricular valves; atrioventricular valves are forced open. As ventricles fill, atrioventricular valve flaps hang limply into ventricles. Atria contract, forcing additional blood into ventricles. (a) AV valves open; atrial pressure greater than ventricular pressure Direction of blood flow Atrium Ventricle Cusp of atrioventricular valve (open) Chordae tendineae Papillary muscle 1 2 3

Copyright © 2011 Pearson Education, Inc. Function of the Atrioventricular Valves Figure 19.7b Ventrles cicontract, forcing blood against atrioventricular valve cusps. Atrioventricular valves close. Papillary muscles contract and chordae tendineae tighten, preventing valve flaps from everting into atria. (b) AV valves closed; atrial pressure less than ventricular pressure Atrium Blood in ventricle Cusps of atrioventricular valve (closed) 1 2 3

Copyright © 2011 Pearson Education, Inc. Function of the Semilunar Valves Figure 19.8 As ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open. As ventricles relax and intraventricular pressure falls, blood flows back from arteries, filling the cusps of semilunar valves and forcing them to close. (a) Semilunar valves open (b) Semilunar valves closed Aorta Pulmonary trunk

Copyright © 2011 Pearson Education, Inc. Heart Sounds “Lub-dup”—sound of valves closing First sound “lub” The AV valves closing Second sound “dup” The semilunar valves closing

Copyright © 2011 Pearson Education, Inc. Heart Sounds Figure 19.6a Pulmonary valve Aortic valve Area of cutaway Mitral valve Tricuspid valve Myocardium Tricuspid (right atrioventricular) valve (a) Mitral (left atrioventricular) valve Aortic valve Pulmonary valve Fibrous skeleton Anterior

Copyright © 2011 Pearson Education, Inc. Heart Sounds Figure 19.9 Tricuspid valve sounds typically heard in right sternal margin of 5th intercostal space Aortic valve sounds heard in 2nd intercostal space at right sternal margin Pulmonary valve sounds heard in 2nd intercostal space at left sternal margin Mitral valve sounds heard over heart apex (in 5th intercostal space) in line with middle of clavicle

Copyright © 2011 Pearson Education, Inc. Blood Flow Through the Heart Figure Right atrium Aorta To body To heart To lungs Mitral valve Left ventricle Left atrium Left atrium Aorta Left ventricle Four pulmonary veins Right ventricle Superior vena cava (SVC) Inferior vena cava (IVC) Coronary sinus Right atrium Pulmonary trunk Pulmonary veins Pulmonary arteries Aortic semilunar valve Tricuspid valve Tricuspid valve Pulmonary trunk Right ventricle Pulmonary semilunar valve Pulmonary semilunar valve IVC SVC Two pulmonary arteries carry the blood to the lungs (pulmonary circuit) to be oxygenated. Oxygen-rich blood returns to the heart via the four pulmonary veins. Oxygen-poor blood returns from the body tissues back to the heart. Oxygen-rich blood is delivered to the body tissues (systemic circuit). Oxygen-rich blood Oxygen-poor blood Mitral valve Aortic semilunar valve Coronary sinus

Copyright © 2011 Pearson Education, Inc. Heartbeat 70–80 beats per minute at rest Systole—contraction of a heart chamber Diastole—expansion of a heart chamber Systole and diastole also refer to Stage of heartbeat when ventricles contract and expand

Copyright © 2011 Pearson Education, Inc. Structure of Heart Wall Left ventricle— three times thicker than right Exerts more pumping force Flattens right ventricle into a crescent shape Figure Right ventricle Left ventricle Interventricular septum

Copyright © 2011 Pearson Education, Inc. Fasciae adherensGap junctions Microscopic Anatomy of Cardiac Muscle Figure NucleusIntercalated discsCardiac muscle cell (a) Nucleus I bandA band Cardiac muscle cell Sarcolemma Z disc Mitochondrion T tubule Sarcoplasmic reticulum I band Intercalated disc (b)

Copyright © 2011 Pearson Education, Inc. Cardiac Muscle Tissue Not all cardiac cells are innervated Will contract in rhythmic manner without innervation Inherent rhythmicity Is the basis for rhythmic heartbeat

Copyright © 2011 Pearson Education, Inc. Conducting System Figure The sinoatrial (SA) node (pacemaker) generates impulses. Internodal pathway Superior vena cavaRight atrium Left atrium Purkinje fibers Inter- ventricular septum The impulses pause (0.1 sec) at the atrioventricular (AV) node. The atrioventricular (AV) bundle connects the atria to the ventricles. The bundle branches conduct the impulses through the interventricular septum. The Purkinje fibers stimulate the contractile cells of both ventricles

Copyright © 2011 Pearson Education, Inc. Thoracic spinal cord The vagus nerve (parasympathetic) decreases heart rate. Cardioinhibitory center Cardio- acceleratory center Sympathetic cardiac nerves increase heart rate and force of contraction. Medulla oblongata Sympathetic trunk ganglion Dorsal motor nucleus of vagus Sympathetic trunk AV node SA node Parasympathetic fibers Sympathetic fibers Interneurons Innervation Heart rate is altered by external controls Nerves to the heart include Visceral sensory fibers Parasympathetic branches of the vagus nerve Sympathetic fibers—from cervical and upper thoracic chain ganglia Figure 19.15