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Learn about the anterior & posterior mediastinum organs, pericardial sac, heart anatomy, and conducting system. Explore heart valves, arterial supply, cardiac nerves, and conducting pathways.
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Operative surgery of heartand organs of mediastinum Associate-professor Kovryha M.F
Radiograph of Chest • T1-body of the first thoracic vertebra • C-clavicle • RA-right atrium • SVC-superior vena cava • IVC-inferior vena cava • A-»aortic knob» • PT-pulmonary trunk • LAA-left auricular appendage • LV-left ventricle
Auscultation points are the areas where sounds from each of the heart's valves may be heard most distinctly through a stethoscope. They do not represent the location of the valves projected on the surface of the chest, although for the tricuspid and pulmonary valves location and sound are quite close. Aortic and mitral valves are deep in the chest and their sounds are heard best at the points where the direction of blood flow is closer to the chest wall. Aortic (A) and Pulmonary (P) areas are in the second interspace to the right and left of the sternal border. The Tricuspid area (T) is near the left sternal border in the 5th or 6th interspace. The Mitral valve (M) is heard best near the apex of the heart in the 5th intercostal space in the midclavicular line.
The Sinu-atrial (SA) Node in the wall of the right atrium near the upper end of the sulcus terminalis and extending over the front of the opening of the superior vena cava. The SA Node is the "pacemaker" of the heart because it initiates cardiac muscle contraction and determines the heart rate. It is supplied by the sinus node artery, usually a branch of the right coronary artery. • Contraction spreads through the atrial wall until it reaches the Atrio-ventricular (AV) Node in the right atrial side of the interatrial septum just above the opening of the Coronary sinus. After a brief delay contraction passes to the ventricles. The AV Node is usually supplied by the distal right coronary artery. • The A V Bundle (B) passes from the AV Node in the membranous part of the interventricular septum and divides into right and left Bundle Branches on either side of the muscular part of the septum. • The right Bundle Branch travels down the septum to the anterior wall of the ventricle, enters the base of the anterior papillary muscle, and excitation spreads to the right ventricular wall. • The left Bundle Branch is a thin, broad band which usually divides into two divisions which enter papillary muscles and excitation of the muscular walls of the left ventricle occurs.
Damage to the conducting system (often by compromised blood supply as in coronary artery disease) leads to disturbances of cardiac muscle contraction. Damage to the AV Node results in "heart block" as the atrial excitation wave does not reach the ventricles which begin to contract independently at their own rate which is slower than that of the atria. Damage to one of the branches results in "bundle branch block" in which excitation goes down the unaffected branch to cause systole of that ventricle. The impulse then spreads to the other ventricle producing later asynchronous contraction.
