Basic Structure of Heart

The heart is small organ about the size of one's fist, located in the middle and slightly to the left of the mediastinum in the chest. The wider top part is the base and the blunt tip projecting forward and to the left if the apex. The heart is enclosed by the pericardium which is thick, fibrous and non-elastic. It consists of two layers: the inner layer-visceral layer and the outer parietal layer. The two pericardial surfaces are separated by a pericardial space that contains approximately 10-20 ml of thin, clear pericardial fluid which acts as a lubricant and reduces friction produced by the pumping action of the heart.

Epicardium-an epithelial single-celled layer surrounding the heart, the innermost layer of the pericardium. Myocardium is the actual heart muscle layer composed of striated muscle fibers. The myocardium is responsible for the energy created to eject a volume of blood. Therefore, it is thicker in the ventricles than in the atria. Endocardium is the inner layer and consists of endothelial tissue lining the entire interior of cardiac chambers and covers the heart valves.