What feature distinguishes myocardium from other heart layers?

The myocardium is specifically distinguished from other layers of the heart by its composition of cardiac muscle. This unique structure allows the myocardium to contract and generate the force necessary to pump blood throughout the body. Unlike the outer layer, which is protective and fibrous, and the inner layer, which is primarily comprised of endothelial cells, the myocardium's muscle tissue is essential for the heart's functionality.

While some other tissues may have varying regenerative capabilities, cardiac muscle does not regenerate easily after injury compared to skeletal muscle, which can lead to significant challenges in heart repair after events such as myocardial infarction. Therefore, the defining feature of the myocardium, setting it apart from other heart layers, is its composition of specialized cardiac muscle tissue.