Abstract:
The heart is one of the most critical organs of the human body.
The function of the heart is the rhythmic pumping of blood. In fact it functions like two pumps - one to move blood into the lungs and
the other to push it into the circulatory system of the body. This function is performed by alternate contraction and relaxation of the muscular structure of its walls. The walls are made of muscle fibres which are the basic functional unit of the muscular system [Refl,7,12 3.
The-heart consists of several layers (Fig 1). The endocardium is the innermost layer which consists of a smooth lining of cells. Such cells are also found in the inside of the blood vessels of the body.
The layer next to endocardium is the myocardium which constitutes the mass of the heart muscle cells. It is their coordinated contraction
and relaxation which causes the chambers of the heart to pump the
blood. The myocardium is thinner in the atria than in the ventricles and thickest in the left ventricle. The myocardium is covered by a
layer of fat called the epicardium. The coronary blood vessels that
supply blood to the heart itself run through this layer. The pericardial sac which encloses the heart is formed by the outermost
two layers of the pericardium which have a small amount of
lubricating fluid between them. Although the heart consists of several layers, it is only the myocardium that generates currents large enough to be detected and recorded on the surface of the body.
