Anatomy of the Heart.pdf

Applied cardiac anatomy cardiovascular system Anatomy of the Heart Heart size approximates a closed fist: 12cm long, 9cm wide, 6cm thick, weighing about 250g. Located in the mediastinum, extending between the sternum and vertebral column, between the lungs. Two-thirds of th...

Applied cardiac anatomy cardiovascular system Anatomy of the Heart Heart size approximates a closed fist: 12cm long, 9cm wide, 6cm thick, weighing about 250g. Located in the mediastinum, extending between the sternum and vertebral column, between the lungs. Two-thirds of the heart's mass is positioned left of the midline. Surface Anatomical Markings Anteriorly situated against the sternum and 3rd to 6th costal cartilages. Upper limit: 3rd costal cartilage at the right sternal edge and 2nd intercostal space at the left. Right margin: spans from 3rd costal cartilage to near the 6th costal cartilage. Inferior margin: runs from the right 6th costal cartilage to the apex (located at the mid-clavicular line, 5th intercostal space). Left margin: stretches from the 2nd intercostal space to the apex. Heart surface anatomical marks: Anterior (sternocostal) surface: right atrium and right ventricle Inferior surface ( diaphragmatic): the right and left ventricles Posterior surface: mainly the left atrium Anatomical Structure of the Heart The heart is encased in the pericardium (membrane surrounding the heart), which anchors it and allows for contractions. Pericardium Parts: o Fibrous layer: tough connective tissue, preventing overstretching. o Serous layer: double-layered, with the outer parietal layer connected to fibrous part and the inner visceral layer (epicardium). Pericardial fluid It lies between the two layers of the serous pericardium It is a lubricating fluid that circulates 30mls; and reduces friction between the 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 Heart Wall Layers – Muscular structure Epicardium: Outer layer composed of visceral serous pericardium, containing adipose tissue and blood vessels that supply the myocardium Myocardium: Cardiac muscle tissue responsible for contraction. Endocardium: Smooth inner lining of chambers and valves. Heart Chambers and Valves The heart consists of four chambers: Two atria (upper) and two ventricles (lower). Applied cardiac anatomy cardiovascular system Sulci: Grooves separating heart chambers (coronary sulcus (encircles most of the heart and divides the atria from the ventricles), anterior and posterior interventricular sulci (divide the two ventricles). Right Atrium Contains pectinate muscles on anterior wall; receives blood from inferior vena cava, superior vena cava, and coronary sinus. Blood flows to the right ventricle through the tricuspid valve. Right Ventricle Features trabeculae carneae (raised bundles of cardiac muscle fibres) and chordae tendineae (tendons connected to the leaflets of the tricuspid valve) connected to papillary muscles (connected to chordae tendinae) Blood exits through the pulmonary valve into the pulmonary trunk. Left Atrium Receives blood from four pulmonary veins and delivers it to the left ventricle via the bicuspid (mitral) valve. Left Ventricle Contains trabeculae carneae and chordae tendineae anchoring mitral valve cusps. Blood exits through the aortic valve into the ascending aorta. Myocardial Thickness Atria: 2-3 mm thick, adequate for low-pressure blood handling to ventricles. Right ventricle: 4-5 mm thick for short-distance pumping to lungs. Left ventricle: 10-15 mm thick for high-pressure pumping to the body. Fibrous Skeleton Dense connective tissue forming the heart's structural foundation, serving as a muscle insertion point and electrical insulator. Applied cardiac anatomy cardiovascular system Valves of the Heart Atrioventricular Valves (Tricuspid & Mitral): Open with high atrial pressure during contraction; close when the ventricle contracts, preventing backflow via chordae tendineae and papillary muscles. Semilunar Valves (Aortic & Pulmonary): Open when ventricular pressure exceeds arterial pressure, preventing backflow during relaxation. 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 Main Great Vessels Superior and Inferior Vena Cava: Deliver deoxygenated blood to the right atrium from the body. Pulmonary Artery: Carries deoxygenated blood from the right ventricle to the lungs for oxygenation. Pulmonary Veins: Transport oxygenated blood from the lungs into the left atrium. Aorta: Distributes oxygenated blood from the left ventricle to systemic circulation. Coronary circulation The left coronary artery passes near the left auricle and divides into after left coronary ostia LAD – left anterior descending: supplies blood to both ventricles – diagonal and septal branches Circumflex brunch – supplies blood to the left ventricle (MV valve) and left atrium The 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 which empties in the right atrium Coronary sinus: drains left and right ventricle and left atrium Middle cardiac vein: drains left and right ventricle Small cardiac vein: drains right atrium and right ventricle Anterior cardiac veins: drains right ventricle and open into the right atrium Applied cardiac anatomy cardiovascular system Applied cardiac anatomy cardiovascular system Pericardium and Heart Wall Copyright 2009, John Wiley & Sons, Inc. Applied cardiac anatomy cardiovascular system