According to About.com, the primary function of the myocardium is to stimulate heart contractions and relaxation. Contractions of the heart allow pumping of blood from the ventricles, and relaxation makes it possible for the atria to receive blood. Without the myocardium, the heart would not beat, and the cells and tissues of the body would not receive blood.
According to Encyclopaedia Britannica, the wall of the heart is composed of three layers, namely the epicardium, myocardium and endocardium. Before reaching the myocardium, the coronary vessels that supply arterial blood to the heart first have to penetrate the epicardium or the outer layer. Basically, the myocardium is the middle layer of cardiac muscles. About.com explains that the spontaneous and involuntary contraction of these cardiac muscle fibers is the function of the peripheral nervous system.
Encyclopaedia Britannica states that there are heart diseases called cardiomyopathies, wherein the myocardium is the layer affected. These heart conditions are different because they do not result from hypertension or from pericardial, valvular or congenital diseases. These types of heart disease can be easily diagnosed because the general symptoms and the blood flow patterns are distinctive. According to Encyclopaedia Britannica, cardiomyopathies are among the primary causes of morbidity and mortality.