Anatomy of the heart

Abstract

<h2>Abstract</h2> The heart is a midline, valvular, muscular pump in the middle mediastinum. It has inferior, left (left ventricle) and right (right atrium) surfaces and a base (facing posteriorly). The intraventricular septum bulges to the left in almost a coronal plane. A figure of eight shaped fibrous skeleton is attached to muscle and valves of the chambers and divides and electrically separates the atria from the ventricles. The pericardium, holding and protecting the heart, has one fibrous and two serous layers. The inferior vena cava passes through the diaphragm at T8 to enter the right atrium with its musculi pectinati in the auricle and the foramen ovale in the fetus. The right ventricle is entered via the tricuspid valve whose 3 cusps are held by papillary muscles and chordae tendineae. The right ventricular wall shows trabeculae carneae and contains the septomarginal trabecula which carries conducting tissue. Blood leaves this chamber via the pulmonary valve. The left atrium receives blood from the lungs via four pulmonary veins. It has musculi pectinati in its auricle. Blood enters the left ventricle, roughened by trabeculae carneae, via the two cusped mitral valve. Specilized cardiac muscle forms the conducting system. Contractions originating at the A-A node under autonomic nervous control spread via the atrial walls to the A-V node, lying between the orifice of the coronary sinus and the septal cusp of the tricuspid valve, and then to the left and right bundles in the intraventricular septum. Purkinje fibres allow spread of excitation to the ventricular walls. The left and right coronary arteries arise from the aortic sinuses. There is poor collateral communication between them. The veins of the heart are variable, mostly ending in the coronary sinus.