Applied Cardiac Anatomy PDF

Anatomy & physiology PHAS5001 Applied Anatomy Cardiovascular system Heart Prof S Ghosh  Learning outcomes Describe the location of the heart within the mediastinum as well as its surface anatomical markings Relate the structure of the heart (its ch...

Anatomy & physiology PHAS5001 Applied Anatomy Cardiovascular system Heart Prof S Ghosh  Learning outcomes Describe the location of the heart within the mediastinum as well as its surface anatomical markings Relate the structure of the heart (its chambers and valves) to its function as a double pump Name the main great vessels Describe the pulmonary circulation and be familiar with the areas of myocardium that this supplies Describe the vasculature related to ECG placement leads  Anatomical location of the heart Roughly the same size of your closed fist: 12cm long, 9 cm wide, 6 cm thick and mass 250g It lies in the mediastinum (from the sternum to the vertebral column, the first rib and between the lungs) 2/3 of the mass lies to the left of the midline Anteriorly: body of the sternum and the 3rd-6th costal cartilages Upper limit: 3rd costal cartilage right sternal edge and 2nd intercostal space at left sternal edge Right margin: from the right 3rd costal cartilage to near the right 6th costal cartilage Inferior margin: sternal end of the right 6th costal cartilage to the apex Apex: mid clavicular line, 5th intercostal space Left margin: from the 2nd intercostal space to the apex  Heart surface anatomical marks Anterior (Sternocostal) surface: right atrium and right ventricle Inferior (Diaphragmatic) surface: the right and left ventricles Posterior surface: mainly the left atrium 3 borders à Pyramidal shape Inferior border Right ventricle Left border Left ventricle + some left atrium Right border Right atrium The apex tip of the left ventricle and rests on the diaphragm The base is formed by the atria Copyright 2009, John Wiley & Sons, Inc.  Anatomical structure of the heart Pericardium - It is the membrane surrounding the heart - It keeps the heart in place while giving enough space for vigorous contractions It consists of 2 parts: 1) Fibrous part: tough and inelastic connective tissue, fusing to the connective tissue of heart/ blood vessels à anchor heart to the mediastinum, prevents overstretching 2) Serous part: thinner layer, double layer The outer parietal layer fused to the fibrous part, the inner visceral layer EPICARDIUM Pericardium and Heart Wall Copyright 2009, John Wiley & Sons, Inc. Pericardial fluid - Between the 2 layers of serous pericardium - A lubricating fluid circa 30mlsà reduces friction between layers as the heart moves Pericarditis Inflammation of the pericardium Various aetiology factors eg. Viral, bacterial; radiation Chest pain extending to the left shoulder and down to the left arm Often mistaken for a heart attack , ST elevation across all leads Pericardial friction rub = heard in 40% of patients; creaking sound heard through a stethoscope  Muscular structures Epicardium (external layer) - Visceral layer of serous pericardium - Contains adipose tissue - Contains blood vessels supplying the myocardium Myocardium Cardiac striated muscle tissue, responsible for the contraction of the heart Endocardium (inner layer) - Endothelium over connective tissue - Smooth lining for the chambers and valves  Chambers of the heart The heart has four chambers: - 2 superior called atria (auricles increase capacity) - 2 inferior called ventricles Sulci: grooves on the surface Coronary sulcus: encircles most of the heart and divides the atria from the ventricles Anterior and posterior interventricular sulci divide the 2 ventricles  Right atrium Anterior wall is rough = Pectinate muscles muscular ridges Interatrial septum a thin wall separates the right and left atrium It receives blood from -inferior vena cava Fossa ovalis -superior vena cava (foramen ovale) -coronary sinus Blood from the right atrium passes into the ventricle through the tricuspid valve (3 cusps)  Right ventricle Trabeculae carneae Raised bundles of cardiac Chordae tendinea muscle fibres ePapillary muscles Chordae tendineae Trabecul ae Tendons connected to the carneae leaflets of the tricuspid valve Papillary muscles Connected to chordae tendineae Interventricular septum divides the 2 ventricles Blood exits the heart through the pulmonary valve into the pulmonary trunk  Left atrium It receives blood from the 4 pulmonary veins Blood passes from the atrium to the ventricle through the bicuspid (mitral) valve (2 cusps)  Left ventricle As the right side it has - trabeculae carneae - chordae tendinae that anchor the cusps of the mitral valve to papillary muscles Blood leaves the ventricle via the aortic valve into the ascending aorta coronary arteries descending aorta  Myocardial thickness The thickness of the myocardium of the 4 chambers varies according to their functions: Atria 2-3 mm of thickness à do not need much pressure to deliver blood to the ventricles Ventricles thicker à need to pump further with higher pressure Right ventricle 4-5 mm short distance (lungs) Left ventricle 10-15 mm great distances (body)  Fibrous skeleton Dense connective tissue that forms a structural foundation, point of insertion for muscle bundles, and electrical insulator between atria and ventricles Copyright 2009, John Wiley & Sons, Inc.  Valves of the heart Atrioventricular valves (Tricuspid and mitral) Blood into atrium = high pressure = contraction à AV valve opens the cusps project into the ventricle Ventricle is relaxed the chordae tendineae are slack and the blood goes from the atrium to low pressure ventricle Ventricle contracts à pressure pulls the cusps upward à they close Papillary muscles contract pulling the chordae tendineae so the cusps cannot open into the atrium à blood does not flow back Copyright 2009, John Wiley & Sons, Inc.  Semilunar valves (Aortic and pulmonary) Ventricles contract = pressure higher than arteries à semilunar valve opens cusps project into the artery lumen The three crescent moon-shaped cusps allow blood to leave the ventricle but they stop a backflow Ventricle relaxes blood starts to flow back filling the cusps which close tightly No valves between veins and atria because blood backflow is reduced the muscles compressing  Main great vessels Five great vessels enter and leave the heart: The superior vena cava and inferior vena cava return deoxygenated blood from the body to the right atrium The pulmonary artery carries deoxygenated blood from the right ventricle into the lungs for oxygenation The pulmonary veins carry oxygenated blood from the lungs into the left atrium The aorta carries oxygenated blood from the left ventricle into systemic circulation. It has many subdivisions: the ascending and descending aorta, the aortic arch, and the thoracic and abdominal aorta  Coronary circulation Coronary arteries Left coronary artery passes near the left auricle and divides into after Left coronary ostia: Left Anterior Descending (LAD): supplies blood to both ventricles – Diagonal and Septal branches Circumflex branch (Cx): supplies blood to the left ventricle (MV valve) and left atrium – divides in Obtuse Marginal branches – usually 2 Right coronary artery supplies small branches to the right atrium and then divides in: Posterior descending artery (PDA): supplies blood to the posterior ventricles and inferior surface Right ventricular branch: supplies blood to the right ventricle anterior surface Coronary veins All the main veins drains into the coronary sinus (posterior face) which empties into the right atrium Principals veins are and they all drain into R atrium: Coronary Sinus: drains left and right ventricle and left atrium Middle cardiac vein: drains left and right ventricles Small cardiac vein: drains right atrium and right ventricle Anterior cardiac veins: drain right ventricle and open into the right atrium