Heart Lecture 23 PDF

Heart Lecture 23 Describe the structure and function of the heart. Describe the coronary vessels. Describe the intrinsic conducting system of the heart. Describe the autonomic innervation of the heart. Describe the great vessels of the heart. Describe the...

Heart Lecture 23 Describe the structure and function of the heart. Describe the coronary vessels. Describe the intrinsic conducting system of the heart. Describe the autonomic innervation of the heart. Describe the great vessels of the heart. Describe the fetal circulation, the changes that occur at birth and the fate of the ductus arteriosus, the ductus venosus, the foramen ovale and the umbilical vessels. Describe the projection of the heart to the anterior thoracic wall in terms of radiographic image and the auscultation of heart sounds.  Thoracic Cavity Viscera Heart The heart is a hollow muscular organ that consists of four chambers. The heart and pericardium are situated obliquely: 2/3 left of Mid- sternal line 1/3 right of Mid- sternal line  Thoracic Cavity Viscera Heart The surfaces of the heart: Anterior surface (sternocostal surface) Formed mainly by right ventricle Right pulmonary surface Formed mainly by right atrium Left pulmonary surface Formed mainly by left ventricle Inferior surface (diaphragmatic surface) Formed mainly by the left ventricle  Thoracic Cavity Viscera Heart The apex of the heart: Inferolateral part of the left ventricle Lies posterior to 5th intercostal space 9cm left of the mid-sternal line  Thoracic Cavity Viscera Heart The base of the heart: Posterior aspect of the heart Formed by the left atrium and part of the right atrium From pulmonary trunk superiorly to coronary groove inferiorly  Thoracic Cavity Viscera Heart The right atrium receives poorly oxygenated blood From superior vena cava SVC and inferior vena cava IVC Blood flows into the right ventricle through the tricuspid valve The right ventricle pumps blood through the pulmonary valve and into the lungs through the pulmonary trunk where it is oxygenated  Thoracic Cavity Viscera Heart The left atrium receives well- oxygenated blood from the lungs through the pulmonary veins Blood flows into the left ventricle through the mitral valve The left ventricle pumps blood through the aortic valve into the aorta for distribution to the entire body  Thoracic Cavity Viscera Heart The cardiac cycle Diastole: Starts with the closure of pulmonary and aortic valves Opening of the atrioventricular valves Atrial contraction Ventricular filling  Thoracic Cavity Viscera Heart Systole: Starts with the closure of the atrioventricular valves Opening of the aortic and pulmonary valves Ventricular contraction  Thoracic Cavity Viscera Heart The myocardium of the heart has a double helical orientation: When the ventricles contract they do not just collapse inward but rather wring themselves out. The coronary sinus separates the atria from the ventricles (arrow). © Sobotta Atlas  Thoracic Cavity Viscera Heart Right Atrium Receives venous blood from SVC and IVC Composed of a right auricle Muscular pouch Extension of the right atrium Overlying the ascending aorta Cells release atrial natriuretic factor Interior of the right atrium Sinus venarum (smooth posterior portion) Where SVC and IVC open Pectinate muscle (rough anterior portion) Right Atrioventricular (AV) orifice  Thoracic Cavity Viscera Heart The smooth and rough parts are separated by a vertical ridge: Crista terminalis (2) The opening for the coronary sinus (7) (venous trunk that receives most of the cardiac veins) Fossa ovalis (interatrial septum separating the artrium) remnant of foramen ovale © 2008 Thieme Publishers  Ductus Arteriosus - Ligamentum Arteriosum Foramen Ovale - Fossa Ovalis  Thoracic Cavity Viscera Heart and great vessels Ligamentum arteriosum A remnant of the ductus arteriosus  Thoracic Cavity Viscera Heart Right Ventricle: Interior composed of muscular elevations: Trabeculae carneae Superiorly it tapers into an arterial cone: Conus arteriosus Leads to the pulmonary trunk Supraventricular ridge  Right Atrio-Ventricular Valve (Tricuspid) Tricuspid valve guards the AV orfice The base of the cusp attached to the fibrous ring The papillary muscle with their chordae tendineae attach the free edge of the cusp to the ventricular wall ( prevents prolapse of cusp)  Thoracic Cavity Viscera Heart Interventricular septum (IVS) Membranous portion / Fibrous portion Muscular portion  Thoracic Cavity Viscera Heart Septomarginal trabecula (moderator band) Muscular bundle from the inferior part of IVS to the base of the anterior papillary muscle The right AV bundle branch is within the band  Pulmonary Valve (semilunar Valve) Three cusp  Thoracic Cavity Viscera Heart Left atrium Receives Four pulmonary veins: Left superior & inferior Right superior & inferior Left auricle Overlaps the root of the pulmonary trunk Contains pectinate muscle AV orifice  Thoracic Cavity Viscera Heart Left ventricle Thick muscular wall Trabeculae carneae Double- leaflet mitral valve (guards the AV orifice) Aortic orifice  Left Atrio-Venticular Valve (Bicuspid) (Mitral) Mitral Valve Anterior and posterior cusp Anterior and posterior papillary muscles with their chordae tendineae  Thoracic Cavity Viscera Heart Mitral Valve Function During diastole: The left ventricle relaxes and the papillary muscle is relaxed The higher pressure from increased blood volume in the left atrium pushes the valve open Mitral Valve Function During systole : The left ventricle contracts and the papillary muscles contract Allowing the cusp to resist the pressure developed in the left ventricle and preventing the cusp from prolapsing into the left atrium  Aortic Valve (semilunar Valve) Three Cusp Semilunar valves: Pulmonary and aortic During diastole: Three concaved cusp catch reverse blood flow Aortic and pulmonary sinuses are a dilations in the wall of the vessel at the attachment of the cusp (mouth of the coronary arteries ) During systole: Cusp are forced © 2008 Thieme Publishers open  Surface Projection aortic pulmonary Left Atrioventricular (mitral) (bicuspid) Right Atrioventricular (tricuspid) Auscultation Site  Thoracic Cavity Viscera Heart Vascularization of the heart: Coronary arteries Cardiac veins Course across the surface of the heart within the epicardium  Thoracic Cavity Viscera Heart and coronary arteries Coronary arteries First branches off aorta Right coronary artery (arises from aortic sinus) Passes between trunk and right auricle Gives off the following branches: Sinoatrial branch Supplies SA node in 60% of the population Right marginal branch Supplies right atrium and ventricle © Dynamic Human Anatomy LWW  Thoracic Cavity Viscera Heart and coronary arteries Coronary arteries First branches off aorta Right coronary artery (arises from aortic sinus) Passes between trunk and right auricle Gives off the following branches: Posterior interventricular branch Descends in the posterior interventricular groove Supplies the right ventricle and part of the left ventricle Supplies the posterior third of the interventricular septum Supplies the AV node in 80% of the population Left ventricular branch Terminal branch © Dynamic Human Anatomy LWW  Thoracic Cavity Viscera Heart and coronary arteries Left coronary artery (arises from the aortic sinus) Passes between the pulmonary trunk and left auricle Divides into two branches: Anterior interventricular branch Anterior IV groove Gives a lateral (diagonal) branch Supplies the adjacent parts of both ventricles. Supplies the anterior two-thirds of the interventricular septum (including the AV bundle)  Thoracic Cavity Viscera Heart and coronary arteries Left coronary artery (arises from the aortic sinus) Passes between the pulmonary trunk and left auricle Divides into two branches: Circumflex branch Follows the coronary groove to the posterior Gives a left marginal branch Supplies the left atrium and ventricle Terminates in the coronary groove on posterior of the heart  Left Coronary Circumflex Marginal Right Coronary Anterior Interventricular (Left Anterior Descending - LAD) Marginal © Dynamic Human Anatomy LWW Thoracic Cavity Viscera Heart and coronary arteries  Venous Drainage of the heart: Most cardiac veins empty into the coronary sinus Runs in the coronary groove Drains into the right atrium © Dynamic Human Anatomy The coronary sinus receives: Great cardiac vein Ascends in anterior IVG Runs in coronary groove Drains the region of the heart supplied by the LCA Middle cardiac vein Ascends in posterior IVG Small cardiac vein Ascends on the right margin © Dynamic Human Anatomy LWW  1. SA node (pacemaker of the heart) SINOATRIAL NODE Anterolateral junction of SVC and right atrium Specialized cardiac muscle cells Initiates an impulse to cardiac ATRIOVENTRICULAR NODE muscles in the atria causing contraction ATRIOVENTRICULAR BUNDLE (BUNDLE OF HIS) RIGHT & LEFT BUNDLE BRANCHES 2. Impulse transmitted to AV node Posterior inferior interatrial septum Distributes the impulse to PURKINJE FIBERS the ventricles through the AV bundle and its branches  3. AV Bundle (Atrioventricular Bundle) SINOATRIAL NODE Purkinje fibers – begins at the AV bundle and passes through the interventricular septum ATRIOVENTRICULAR (IVS) where it divides into left NODE and right bundle branches ATRIOVENTRICULAR BUNDLE (BUNDLE OF HIS) RIGHT & LEFT BUNDLE BRANCHES 4. Left & Right Bundle Branches Purkinje fibers – along the side of the IVS and pass around the apex of the PURKINJE FIBERS heart to supply the muscles of the ventricle and the papillary muscles  Thoracic Cavity Viscera Innervation of the Heart Innervation of the heart: Through cardiac plexus which consist of autonomic fibers Cardiac Plexus: Superficial Plexus – anterior to the arch of the aorta Deep Plexus lying on the anterior surface of the trachea Formed of both parasympathetic and sympathetic fibers. Autonomic fiber are distributed to: Coronary vessels SA & AV node © Dynamic Human Anatomy LWW  Thoracic Cavity Viscera Innervation of the Heart Sympathetic Motor: 1. Preganglionic neurons originate at the spinal cord's T1-T5 intermediolateral column (nucleus) and their axons exit the ventral root as they course to the sympathetic chain. 2. Postganglionic neurons originate at the lower cervical & upper thoracic ganglia of the sympathetic chain and their axons innervate the: 1. SA and AV node. 2. General myocardium (left ventricle most prominent) 3. Coronary arteries 3. Function: 1. Increase heart rate and force of muscle contraction 2. Dilation of coronary arteries  Thoracic Cavity Viscera Innervation of the Heart Parasympathetic Motor: 1. Preganglionic neurons originate in the medulla (Nucleus Ambiguus & Dorsal Vagal Nucleus) and their axons course within the Vagus nerve to synapse on: 1. Postganglionic neurons located in the cardiac plexus or posterior aspect of the arterial walls. 2. Postganglionic neurons and their axons innervate the: 1. SA and AV node. 2. General myocardium (left ventricle most prominent) – minimally 3. Coronary arteries – minimally 3. Function: 1. Decrease heart rate 2. Constricts of coronary arteries