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Transcript
Chambers, conduction system and nerves of the heart Dr. Muddanna S. Rao Associate Professor Department of Anatomy, Faculty of Medicine, Kuwait University, Kuwait Chambers, conduction system and nerves of the heart Objectives: 1. Differentiate between chambers of heart 2. Describe salient features of right and left atria and ventricles. 3. Relate structure and functions of heart valves 4. Describe the position of heart valves and relate with projection of heart sounds 5. Describe the conduction system of heart. 6. Describe the components of cardiac plexus and innervation pattern of heart Chambers of the heart Sternocostal surface Base and diaphragmatic surface Left ventricle Left ventricle Right ventricle On the external surface of human heart four chambers of the heart can be identified - 2 Atria (Left atrium and right atrium) and 2 ventricles (Left ventricle and right ventricle. Chambers of the heart (opened) In schematic section of human heart, four chambers are shown-Left atrium, right atrium, Left ventricle and right ventricle. Right atrium receives the deoxygenated blood through superior and inferior vena cava. Superior vena cava brings the blood from upper limbs, head and neck region, and inferior vena cava from trunk and lower Limbs. Blood from right atrium flows into right ventricle through right atrioventricular orifice. From the right ventricle blood flows through pulmonary trunk into left and right lungs for oxygenation(pulmonary circulation). Left atrium receives the oxygenated blood from left and right lungs through pulmonary veins. Through left atrioventricular / mitral orifice blood flows into left ventricle, and from here it flows through ascending aorta for distribution to various parts of the body (Systemic circulation). Right Atrium Right auricle Interatrial septum Superior vena cava Right atrioventricular orifice Limbus fossa ovalis Fossa ovalis Musculi pectinati Cresta terminalis Opening of coronary sinus Left ventricle Inferior vena cava Valve of inferior vena cava and coronary sinus Right atrium receives deoxygenated blood from various parts of the body through SVC and IVC and coronary sinus. Interior of the right atrium shows thin walled smooth posterior part, Sinus venarum and rough anterior part. The rough part consists of a muscular ridge, called cresta terminalis (corresponding to sulcus terminalis on the external surface) and muscular ridges arising from it - musculi pectinati. In the interatrial septum, Limbus fossa ovalis, bounds the fossa ovalis, an oval depression. Coronary sinus opens into right atrium between opening of the IVC(Guarded and is guarded by its valve), and atrioventricular orifice.It is guarded by valve of coronart sinus. Tricuspid (Right atrioventricular)valve Right atrium Right Ventricle Cusps of tricuspid valve The tricuspid (right atrioventricular) orifice is guarded by tricuspid valve.This valve has anterior, posterior and septal cusps.The cusps are thin double foildings of endocardium. The chordae tendinae arising from the papillary muscles are attached to the fee margin and ventricular surface of the cusp and prevent the prolapse of the cusps into atria during systole. They prevent backflow of blood into atria during ventricular systole. Right Ventricle Supraventricular crest Pulmonary trunk Pulmonary valve Infundibulum Right atrium Interventricular septum Right ventricle Tricuspid (right atrioventricular valve Muscle ridges Chordae tendinae Septomarginal band (Moderator band) Papillary muscles Muscle bridges Interior of the right ventricle shows rough inflow part and smooth outflow partinfundibulum. Infundibulum is separated from rest of the ventricle by supraventricular crest, a muscular ridge. The rough part has the cardiac muscles arranged in the form of papillary muscles (Anterior, posterior, and septal), ridges and bridges. Chordae tendinae connect the papillary muscles to cusps of tricuspid orifice. Septomarginal band stretches from interventricular septum to the base of anterior papillary muscle. Infundibulum leads to pulmonary trunk, guarded by pulmonary valve. Pulmonary Valve Pulmonary Valve Pulmonary sinus Similunar Cusps The pulmonary orifice is guarded by pulmonary valve. It has 3 semilunar cuspsAnterior, right posterior, left posterior. Pulmonary valve prevent backflow of blood during ventricular diastole. Left Atrium Arrow in the left atrioventricular (bicuspid) orifice Left auricle Left Atrium Pulmonary veins Left Atrioventricular (bicuspid) Valve Interatrial septum (Region of fossa ovalis) Interior of the left atrium shows thin walled smooth posterior part, and rough anterior part- auricle. In the interatrial septum, impression of limbus fossa ovalis, and fossa ovalis, (which are seen in right atrium) can be seen. Left atrium receives oxygenated blood from lungs through four pulmonary veins. Blood leaves the atrium through left atrioventricular orifice (Mitral orifice) to reach left ventricle. Bicuspid/mitral (Left atrioventricular)valve Left atrium Chordae Tendinae Left ventricle Cusps of mitral valve Papillary muscle The bicuspid (left atrioventricular) orifice is guarded by mitral valve. They prevent backflow of blood into atria during ventricular systole. This valve has anterior and posterior cusps. The chordae tendinae, attached to the fee margin and ventricular surface of the cusp, prevent their prolapse into left atrium during systole. Chordae tendinae Left Ventricle Arrow in the left atrioventricular (bicuspid) orifice Papillary muscle Left Atrium Aortic valve Left Ventricle Left Atrioventricular (bicuspid) Valve Thick wall Aortic vestibule Left ventricle receives oxygenated blood from left atrium through left atrioventricular orifice, and pumps the blood into aorta through arortic orifice. Interior of the left ventricle shows rough in flow part and smooth outflow part- aortic vestibule. The rough part has the cardiac muscles arranged in the form of papillary muscles (Anterior and posterior), ridges and bridges. Chordae tendinae connect the cusps of the valve to papillary muscle. Aortic vestibule leads to ascending aorta, guarded by aortic valve. Aortic Valve Aortic valve Aortic sinus Coronary artery Semilunar cusp The aortic orifice is guarded by aortic valve. It has 3 semilunar cusps-right, left and posterior. Left and right coronary arteries arise from left and right aortic sinus respectively. Aortic valve prevent backflow of blood during ventricular diastole. Interatrial septum Interatrial septum Interatrial septum (From right side) Limbus fossa ovalis Fossa ovalis Interatrial septum (From left side) The interatrial septum is the thin partition between left and right. Fossa vovalis and limbus fossa vovalis can be seen on the right side of the septum Interventricular septum Membranous part of interventricular septum Interventricular septum Left ventricle Right ventricle Left ventricle Right ventricle Muscular part of interventricular septum The interventricular septum, the partition between left and right ventricles, has membranus and muscular parts. Interventricular septum is convex towards right ventricle. Cavity of the right ventricle is crescentic and left ventricle is circular in cross section. Wall of left ventricle is 3 times thicker than right ventricle. Valves of the heart seen from Above during diastole and systole Diastole Anterior Systole Left Right Posterior A R L L R P Pulmonary orifice Aortic orifice Tricuspid orifice Bicuspid (Mitral)orifice During diastole, ventricles (Left and right) relax, the right and left atrioventricular orifice open allowing the blood to flow from atria to ventricles. During this time pulmonary and aortic orifices are closed, preventing the backflow of blood into the ventricles. Bicuspid (Mitral)orifice Tricuspid orifice During systole, ventricles (Left and right) contract, the right and left atrioventricular orifice are closed preventing back flow of blood into to atria. During this time pulmonary and aortic orifices are open, allowing the flow of blood into pulmonary trunk and aorta. Surface projection of of heart orifices Site of auscultation of valve Sites of heart sound A- Aortic P - Pulmonary T - Tricuspid M – Mitral Cardiac orifices a- aortic p - Pulmonary t - Tricuspid m - Mitral Location of valve A p a P t m T M The right and left atrioventricular,aortic and pulmonary orifices can be depicted on the surface of chest along an oblique line from left 3rd sternocostal joint(costal cartilage) to right sternal margin at 4th intercostal space. Pulmonary orifice on left 3rd costal cartilage, Aortic orifice on body of the sternum at level of 3rd intercostal space. Left atrioventricular (Mitral orifice) on left sternal margin across the 4th sternocostal joint (costal cartilage). Right atrioventricular orifice on the right margin of sternum at 4th intercostal space. Sites of heart sound A- Aortic P - Pulmonary T - Tricuspid M – Mitral Cardiac orifice a- aortic p - Pulmonary t - Tricuspid m - Mitral Location of valve Sites of heart sounds Site of auscultation of valve A p a P t m T M When the blood flows through left and right atrioventricular, aortic and pulmonay orifice, they produce the heart sounds, which can be heard better on certain points on the chest wall. The left atriovetriculr (mitral) valve sound best heard in the left 5th intercostal space, in the midclavicular line. The right atriovetriculr (tricuspid) valve sound best heard along the left sternal margin at 6th sternocostal joint. Aortic and pulmonary valve sound along the right and left margin of sternum at the level of the second intercostal space respectively. Position of heart valves and projection of heart sounds Site of auscultation of valve A p a T p M A P t m Location of valve T M When the blood flows through left and right atrioventricular, aortic and pulmonay orifice, they produce the heart sound, which can be heard better in the direction of blood flow. Conducting system of the Heart Left branch of bundle of His and its branches on left side of interventricular septum Sinuatrial node Bundle of His Left branch of His Left ventricle Right branch of bundle of His on right side of interventricular septum Atrioventricular node Conducting system of heart is specialized cardiac muscle tissue, concerned with generation and propagation of cardiac impulses. This system is responsible for highly rhythmic contraction and relaxation of heart muscle. Autononic nerves influence the cnducting system. Conducting system includes Sinuatrial node(SA node),atrioventricular node(AV node),bundle of His, left and right branches of bundle of His and their further branches, purkinje fibers.SA node is pacemaker of the heart, is situated in the right atrial wall close to superior vena caval entry. AV node is situated posteroinferior region of interatrial septum, near the opening of coronary sinus. Bundle of his passes through the fibrous skeleton of the heart and reaches the right side of interventricular septum, where it divides into left and right branches. Right runs on the right side of interventricular septum and divides into several branches and end in purkinje fibers, which supply the ventricular muscles and papillary muscles. Left branch runs on the left side of interventricular septum and divides into its branches finally end in purkinje fibers, suppling left ventricular and papillary muscles. Conducting system of the Heart Impulses (arrows) initiated at the SA node, located at the superior end of the sulcus (internally, crista) terminalis, are propagated through the atrial musculature to the AV node. Impulses (arrows) received by the AV node, in the inferior part of the interatrial septum, are conducted through the AV bundle and its branches to the myocardium. The AV bundle begins at the AV node and divides into right and left bundles at the junction of the membranous and muscular parts of the interventricular septum. Parasympathetic nucleus of vagus nerve Innervation of the Heart Cervical ganglia of sympathetic chain Vagus nerve Cardiac branches of vagus nerve Cardiac branches from sympathetic ganglion Thoracic sympathetic ganglia Trachea Superficial cardiac plexus on arch of aorta Deep cardiac plexus Thoracic segments of spinal cord Heart Innervation of the Heart Heart is innervated by Autonomic nervous system. Sympathetic, parasympathetic and cardiac afferent nerve fibers form the superficial cardiac plexus (on the arch of the aorta) and deep cardiac plexus (behind the ascending aorta and pulmonary trunk, in front of bifurcation of trachea). Nerves from these plexus supply the heart. Sympathetic: Preganglionic sympathetic fibers arise from the lateral horn of upper 5-6 thoracic spinal segments of the spinal cord. Post ganglionic fibers run through cardiac branches of cervical sympathetic and superior thoracic ganglion and reach the cardiac plexus. They innervate the SA node, AV node and coronary arteries. Sympathetic stimulation causes increased heart rate , impulse conduction, force of contraction and increased blood flow through coronary arteries. Parasympathetic: Preganglionic parasympathetic fibers arise from parasympathetic nucleus of vagus nerve and pass through the carddiac braches of vagus nerve and reach the cardiac plexus. Postsynaptic parasympathetic cell bodies are located in the atrial wall, interatrial septum near SA and AV nodes and along the coronary arteries. Parasympathetic stimulation slows the heart rate, reduces the force of contraction, constricts the coronary artery. Ref: 1.Clinically oriented Anatomy ,6th Ed. By Keith L. More, Arthur F. Dalley and Anne M.R. Agur 1.Grays Anatomy, 38TH Ed. By Peter L. Williams et al Thank you