Briefly describe the structure of the heart.

A hollow muscular organ consisting of two atria and two ventricles. The wall of the heart is represented by the epicardium – the connective tissue membrane, the myocardium – the muscular membrane of the striated cardiac muscle tissue, and the endocardium, the inner membrane. The pericardium forms a pericardial sac, the inner layer of which secretes serous fluid, which reduces the frictional force during muscle contractions. The aorta departs from the left ventricle, the pulmonary artery departs from the right ventricle.