What is the muscular layer of the heart called?

The muscular layer of the heart is known as the myocardium. It is responsible for the heart's contractile function, enabling it to pump blood throughout the body. The myocardium is composed mainly of cardiac muscle tissue, which is specialized for continuous rhythmic contractions throughout a person's life. This layer is thickest in the ventricles, as these chambers need to generate more force to pump blood out of the heart and into the systemic and pulmonary circulations.

In contrast to the myocardium, the endocardium is the inner lining of the heart chambers, providing a smooth surface for blood flow. The epicardium is the outer layer of the heart, also considered a part of the pericardium, which is a protective sac surrounding the heart. The pericardium itself has a fibrous outer layer and a serous inner layer but does not contribute to the heart's pumping action. Understanding these structures helps clarify the unique roles each layer plays in the overall function of the heart.