Anatomy The heart is enveloped in a layer of fibrous pericardium and lies between the lungs. Inferiorly is the diaphragm. Posteriorly the descending aorta and oesophagus. The heart is a conical shaped structure with both an apex and base lying in the middle of the mediastinum. The apex of the cone points down and out and its anatomical surface marking is the mid clavicular line in the 5th Intercostal space. The base of the pyramid faces posteriorly. The heart is made up of 4 chambers. The two atria acts as storage vessels for blood returning to the heart. The two ventricles act as pumps. On the left side the left atrium receives oxygenated blood from the lungs from the four pulmonary veins. The left atrium and left ventricle are separated by the semilunar mitral valve. The mitral valve has anterior and posterior leaflets. The left ventricle pumps blood into the systemic circulation and has a thick muscular wall On the right side the right atrium receives deoxygenated blood from the systemic circulation from the inferior and superior vena cavae. The right atrium and ventricle separated by tricuspid valve which has three leaflets. Blood is ejected with systole across the pulmonary valve into the pulmonary artery. Right sided pressures are low and the RV is thin walled compared with the left. The right border of the heart is formed almost entirely by the right atrium. The left border of the heart is formed almost entirely by the left ventricle with the left atrial appendage superiorly. The base or posterior surface is formed almost entirely by the left atrium which is closely opposed to the oesophagus (important for transoesophageal echo). Inferior or diaphragmatic surface of the heart is made up by the right and left atrium
Posted on: Wed, 27 Aug 2014 06:00:00 +0000
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