MEDIASTINUM G.LUFUKUJA

The mediastinum The mediastinum is the central compartment of the thoracic cavity  that contains a group of structures within the thorax. The mediastinum contains the heart and its vessels, the esophagus, trachea, phrenic and cardiac nerves, the thoracic duct, thymus and lymph nodes of the central chest G.LUFUKUJA

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MEDIASTINUM: The superior mediastinum The mediastinum is artificially divided into superior and inferior parts for purposes of description. The superior mediastinum extends inferiorly from the superior thoracic aperture to the horizontal plane that includes the sternal angle anteriorly and passes approximately through the junction (IV disc) of the T4 and T5 vertebrae posteriorly, often referred to as the transverse thoracic plane G.LUFUKUJA

Contents of the superior mediastinum It contains the lower ends of sternohyoid, sternothyroid on each side; the aortic arch; the brachiocephalic artery and the thoracic portions of the left common carotid and left subclavian arteries; the brachiocephalic veins and the upper half of the superior vena cava; the vagus, cardiac, phrenic and left recurrent laryngeal nerves; the trachea, oesophagus, and thoracic duct; the remains of the thymus, and lymph nodes. G.LUFUKUJA

The inferior mediastinum The inferior mediastinum is further subdivided by the pericardium into anterior, middle, and posterior parts. The pericardium and its contents (the heart and roots of its great vessels) constitute the middle mediastinum. Some structures, such as the esophagus, pass vertically through the mediastinum and therefore lie in more than one mediastinal compartment. G.LUFUKUJA

Contents of the anterior mediastinum: Sternopericardial ligaments Retro-sternal lymph nodes Branches of Internal thoracic artery G.LUFUKUJA

MIDDLE MEDIASTINUM: The middle mediastinum contains the heart enclosed in the fibrous pericardium, the ascending aorta, the lower half of the superior vena cava with the azygos vein opening into it, the bifurcation of the trachea and the right and left principal bronchi, the pulmonary artery dividing into its two branches, the right and left pulmonary veins and phrenic nerves, and some bronchial lymph nodes. G.LUFUKUJA

Pericardium… Nerve Supply The fibrous pericardium and the parietal layer of the serous pericardium are supplied by the phrenic nerves. The visceral layer of the serous pericardium is innervated by branches of the sympathetic trunks and the vagus nerves G.LUFUKUJA

Applied Anatomy Pericarditis Pericarditis is swelling and irritation of the pericardium, the thin sac-like membrane surrounding your heart. Pericarditis often causes chest pain and sometimes other symptoms. The sharp chest pain associated with pericarditis occurs when the irritated layers of the pericardium rub against each other. In pericarditis pericardial fluid may also accumulate excessively, which can compress the thin-walled atria and interfere with the filling of the heart during diastole. This compression of the heart is called cardiac tamponade. Cardiac tamponade (heart compression) is a potentially lethal condition because the fibrous pericardium is tough and inelastic G.LUFUKUJA

POSTERIOR MEDIASTINUM: It contains the descending thoracic aorta and the azygos, hemiazygos and accessory azygos veins; the right and left sympathetic chains, the splanchnic nerves and the right and left vagus nerves; the oesophagus; the thoracic duct and posterior mediastinal lymph nodes. G.LUFUKUJA

HEART & GREAT VESSELS G.LUFUKUJA

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EXTERNAL FEATURES Atrioventricular groove (coronary sulcus) Interventricular groove Auricles – extensions of each atria G.LUFUKUJA

Borders: Superior, Inferior, Right , Left SURFACES AND BORDERS: Surfaces: Anterior (Sternocostal) & Inferior (diaphragmatic) Borders: Superior, Inferior, Right , Left APEX: Formed by the left ventricle, Located in the left 5th intercostal space Just medial to the midclavicular line G.LUFUKUJA

BASE: Formed by the left atrium and a small part of the right atrium; Openings of four pulmonary veins & Openings of superior and inferior vena cavae G.LUFUKUJA

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ARTERIAL SUPPLY TO THE HEART Right and Left coronary arteries G.LUFUKUJA

RCO LCO TCAO RAV LAV G.LUFUKUJA

AA LCA G.LUFUKUJA

VENOUS DRAINAGE OF THE HEART G.LUFUKUJA

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Applied Anatomy Angina pectoris – commonly known as angina – is chest pain due to ischemia of the heart muscle, generally due to obstruction or spasm of the coronary arteries. The main cause of Angina pectoris is coronary artery disease, due to atherosclerosis of the arteries feeding the heart G.LUFUKUJA

RIGHT ATRIUM Receives venous blood from the whole body & Sends it to the right ventricle through the tricuspid orifice G.LUFUKUJA

Sinus venarum RIGHT ATRIUM – INTERNAL FEATURES Divided into three parts Smooth posterior wall – sinus venarum Rough anterior wall – pectinate part Septal wall Musculi pectinati Crista terminalis Fossa ovalis Sinus venarum Superior vena cava Inferior vena cava Coronary sinus Thebasian valve Eustachian valve G.LUFUKUJA

Receives blood from the right atrium & Pumps it through the pulmonary trunk to the lungs RIGHT VENTRICLE Chordae tendinae – Strings that attach the tips of the papillae to the free edges of the cusps Have trabeculae carneae G.LUFUKUJA

LEFT ATRIUM Receives the four pulmonary veins Most of the interior is smooth Musculi pectinati are present only in the left auricle Fossa lunata – corresponds to the fossa ovalis G.LUFUKUJA

LEFT VENTRICLE Interior has a rough inflow part and a smooth outflow part Inflow part has trabeculae carneae G.LUFUKUJA

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Lymphatic drainage Subendocardial plexus myocardial plexus subpericardial plexus bronchomediastinal trunks G.LUFUKUJA

Nerve supply of heart Nerve of the heart are derived from cardiac plexus, which is formed by the sympathetic and parasympathetic (vagal) fibres. cardiac plexus G.LUFUKUJA G.LUFUKUJA 33

Effect of sympathetic and parasympathetic fibres Sympathetic fibres supply the atria,ventricles and conducting system of heart. -sympathetic stimulation lead to (a) increase in heart rate. (b) increase in cardiac output. (c) vasodilation of coronary artery. 2) Parasympathetic will do the reverse G.LUFUKUJA

Conducting system of the heart 1) Sinuatrial node ( SA node) 2) Atrioventricular Bundle(AV Bundle of HIS) 3) Right and left branches G.LUFUKUJA

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Applied anatomy- arrhythmias Failure of the Conduction System of the Heart The sinuatrial node is the spontaneous source of the cardiac impulse. The atrioventricular node is responsible for picking up the cardiac impulse from the atria. The atrioventricular bundle is the only route by which the cardiac impulse can spread from the atria to the ventricles. Failure of the bundle to conduct the normal impulses results in alteration in the rhythmic contraction of the ventricles (arrhythmias) or, if complete bundle block occurs, complete dissociation between the atria and ventricular rates of contraction. The common cause of defective conduction through the bundle or its branches is atherosclerosis of the coronary arteries, which results in a diminished blood supply to the conducting system. G.LUFUKUJA

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