Chapter 19 (The Heart) PDF

CHAPTER 19 The Heart Human Anatomy Copyright Copyright©©2011 2011Pearson PearsonEducation, Educatio, Inc. Inc. The Heart A muscular double pump Pulmonary circuit takes blood to and from the lungs Systemic circuit transport blood to and from body tissues Atria receive blood Ventricles pumping chamber...

CHAPTER 19 The Heart Human Anatomy Copyright Copyright©©2011 2011Pearson PearsonEducation, Educatio, Inc. Inc. The Heart A muscular double pump Pulmonary circuit takes blood to and from the lungs Systemic circuit transport blood to and from body tissues Atria receive blood Ventricles pumping chambers of the heart The Pulmonary and Systemic Circuits Capillary beds of lungs where gas exchange occurs Pulmonary Circuit Pulmonary arteries Pulmonary veins Aorta and branches Venae cavae Left atrium Right atrium Left ventricle Heart Right ventricle Oxygen-rich, CO2-poor blood Oxygen-poor, CO2-rich blood Systemic Circuit Capillary beds of all body tissues where gas exchange occurs Location and Orientation within the Thorax Midsternal line Superior vena cava Aorta Parietal pleura (cut) Pulmonary trunk Left lung Pericardium (cut) Rib 2 Apex of heart Diaphragm Diaphragm (c) (a) Mediastinum Mediastinum Superior vena cava Heart Right lung (b) Posterior Right auricle of right atrium Right ventricle (d) Aorta Left lung Fat in epicardium Rib 5 Pericardium (cut) Apex of heart 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 Midsternal line Rib 2 Inferior left lies in the fifth intercostal space at the midclavicular line Diaphragm (a) Structure of the Heart – Coverings Pericardium Fibrous pericardium strong layer of dense connective tissue Serous pericardium formed from two layers Structure of the Heart – Layers of the Heart Wall Epicardium visceral layer of the serous pericardium Myocardium consists of cardiac muscle arranged in circular and spiral patterns Endocardium endothelium resting on a layer of connective tissue lines the internal walls of the heart Structure of the Heart – Layers of the Heart Wall Cardiac muscle bundles Heart Chambers Internal divisions Atria and ventricles Interventricular and interatrial septa External markings Coronary sulcus Anterior and posterior interventricular sulcus Heart Chambers Brachiocephalic trunk Left common carotid artery Left subclavian artery Superior vena cava Aortic arch Ligamentum arteriosum Right pulmonary artery Left pulmonary artery Ascending aorta Pulmonary trunk Left pulmonary veins Right pulmonary veins Right atrium Right coronary artery (in coronary sulcus) Anterior cardiac vein Auricle of left atrium Circumflex artery Left coronary artery (in coronary sulcus) Left ventricle Right ventricle Inferior vena cava Great cardiac vein Anterior interventricular artery (in anterior interventricular sulcus) (b) Anterior view Apex Right marginal artery Small cardiac vein Heart Chambers Aorta Superior vena cava Right pulmonary artery Pulmonary trunk Right atrium Left pulmonary artery Left atrium Left pulmonary veins Mitral (bicuspid) valve Right pulmonary veins Fossa ovalis Pectinate muscles Tricuspid valve Right ventricle Chordae tendineae Trabeculae carneae Inferior vena cava (e) Frontal section Aortic valve Pulmonary valve Left ventricle Papillary muscle Interventricular septum Epicardium Myocardium Endocardium Inferior View of the Heart Aorta Left pulmonary artery Superior vena cava Right pulmonary artery Right pulmonary veins Left pulmonary veins Auricle of left atrium Left atrium Right atrium Inferior vena cava Great cardiac vein Posterior vein of left ventricle Left ventricle Coronary sinus Right coronary artery (in coronary sulcus) Posterior interventricular artery (in posterior interventricular sulcus) Middle cardiac vein Right ventricle Apex (d) Inferior view; surface shown rests on the diaphragm. Pathway of Blood Through the Heart Begin oxygen-poor blood in the superior and inferior venae cavae PLAY Go through pulmonary and systemic circuits Heart Blood Flow Blood Flow Through the Heart Superior vena cava (SVC) Inferior vena cava (IVC) Coronary sinus SVC Right atrium Tricuspid valve Right ventricle Pulmonary semilunar valve Pulmonary trunk Pulmonary trunk Coronary sinus Tricuspid valve Right atrium IVC Pulmonary semilunar valve Right ventricle Two pulmonary arteries carry the blood to the lungs (pulmonary circuit) to be oxygenated. Oxygen-poor blood To heart returns from the body tissues back to the heart. To lungs Pulmonary arteries Oxygen-rich blood Oxygen-poor blood To body Oxygen-rich blood is delivered to the body tissues (systemic circuit). Oxygen-rich blood returns To heart to the heart via the four pulmonary veins. Aorta Mitral valve Left ventricle Aortic semilunar valve Aorta Aortic semilunar valve Pulmonary veins Left atrium Left ventricle Mitral valve Left atrium Four pulmonary veins Heartbeat 70–80 beats/minute at rest Systole – contraction Diastole – expansion Systole and diastole also refer to: Stage of heartbeat when ventricles contract and expand Structure of Heart Wall Walls differ in thickness PLAY Atria – thin walls Ventricles – thick walls Heart Anatomy Structure of Heart Wall Left ventricle – three times thicker than right Exerts more pumping force Left ventricle Right ventricle Interventricular septum Heart Valves – Valve Structure Each valve composed of: Endocardium with connective tissue core Atrioventricular (AV) valves between atria and ventricles Aortic and pulmonary valves PLAY at junction of ventricles and great arteries Heart Valves Heart Valves – Valve Structure Pulmonary valve Aortic valve Area of cutaway Mitral valve Myocardium Tricuspid valve Tricuspid (right atrioventricular) valve Mitral (left atrioventricular) valve Aortic valve Pulmonary valve Fibrous skeleton (a) Anterior Function of the Atrioventricular Valves 1 Blood returning to the heart fills atria, putting pressure against atrioventricular valves; atrioventricular valves are forced open. 2 As ventricles fill, atrioventricular valve flaps hang limply into ventricles. 3 Atria contract, forcing additional blood into ventricles. Direction of blood flow Atrium Cusp of atrioventricular valve (open) Chordae tendineae Ventricle (a) AV valves open; atrial pressure greater than ventricular pressure Papillary muscle Function of the Atrioventricular Valves 1 Ventrles contract, forcing blood against atrioventricular valve cusps. 2 Atrioventricular valves close. 3 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 Cusps of atrioventricular valve (closed) Blood in ventricle Function of the Semilunar Valves Aorta Pulmonary trunk As ventricles contract and intraventricular pressure rises, blood is pushed up against semilunar valves, forcing them open. (a) Semilunar valves open As ventricles relax and intraventricular pressure falls, blood flows back from arteries, filling the cusps of semilunar valves and forcing them to close. (b) Semilunar valves closed Heart Sounds “Lub-dup” – sound of valves closing First sound “lub” – the AV valves closing Second sound “dup” – the semilunar valves closing Heart Sounds Each valve sound – best heard near a different heart corner Pulmonary valve – superior left corner Aortic valve – superior right corner Mitral (bicuspid) valve– at the apex Tricuspid valve – inferior right corner Heart Sounds 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 Tricuspid valve sounds typically heard in right sternal margin of 5th intercostal space Conducting System Cardiac muscle tissue has intrinsic ability to: Generate and conduct impulses Signal these cells to contract rhythmically Conducting system A series of specialized cardiac muscle cells Sinoatrial (SA) node sets the inherent rate of contraction Conducting System Superior vena cava Right atrium 1 The sinoatrial (SA) node (pacemaker) generates impulses. Internodal pathway 2 The impulses pause (0.1 sec) at the atrioventricular (AV) node. Left atrium 3 The atrioventricular Purkinje fibers 4 The bundle branches Interventricular septum (AV) bundle connects the atria to the ventricles. conduct the impulses through the interventricular septum. 5 The Purkinje fibers stimulate the contractile cells of both ventricles. Conduction System of the Heart 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 The vagus nerve (parasympathetic) decreases heart rate. Dorsal motor nucleus of vagus Cardioacceleratory center Sympathetic trunk ganglion Cardioinhibitory center Medulla oblongata Thoracic spinal cord Sympathetic trunk Sympathetic cardiac nerves increase heart rate and force of contraction. AV node SA node Parasympathetic fibers Sympathetic fibers Interneurons Blood Supply to the Heart Functional blood supply Coronary arteries Arise from the aorta Located in the coronary sulcus Main branches Left and right coronary arteries Blood Supply to the Heart Aorta Pulmonary trunk Left atrium Superior vena cava Anastomosis (junction of vessels) Left coronary artery Right atrium Right coronary artery Right ventricle Circumflex artery Left ventricle Right marginal artery Anterior interventricular artery Posterior interventricular artery (a) The major coronary arteries Superior vena cava Great cardiac vein Anterior cardiac veins Coronary sinus Small cardiac vein Middle cardiac vein (b) The major cardiac veins Coronary Bypass The Heart Throughout Life Arterial end 4a 4 Tubular heart Arterial end Ductus arteriosus Inferior vena cava Ventricle Ventricle Atrium 3 2 Pulmonary trunk Foramen ovale Ventricle 1 (a)Day 20: Endothelial tubes begin to fuse. Aorta Superior vena cava (b) Day 22: Heart starts pumping. Venous end (c) Day 24: Heart continues to elongate and starts to bend. Venous end (d) Day 28: Bending continues as ventricle moves caudally and atrium moves cranially. (e) Day 35: Bending is complete. Congenital Heart Defects Narrowed aorta Occurs in about 1 in every 500 births Occurs in about 1 in every 1500 births (a) Ventricular septal defect. (b) Coarctation of the aorta. A part of the aorta is narrowed, The superior part of the interincreasing the workload of ventricular septum fails to form; the left ventricle. thus, blood mixes between the two ventricles. More blood is shunted from left to right because the left ventricle is stronger. Occurs in about 1 in every 2000 births (c) Tetralogy of Fallot. Multiple defects (tetra = four): (1) Pulmonary trunk too narrow and pulmonary valve stenosed, resulting in (2) hypertrophied right ventricle; (3) ventricular septal defect; (4) aorta opens from both ventricles.