What is the main characteristic of the myocardium?

The myocardium is the thick, muscular middle layer of the heart wall, primarily composed of cardiac muscle tissue, which is responsible for the heart's ability to pump blood throughout the body. This layer makes up approximately 95% of the heart's structure, allowing it to contract and generate the force necessary for blood circulation. The unique properties of cardiac muscle, such as its involuntary nature and ability to conduct electrical impulses, enable the heart to function efficiently as a vital organ in the circulatory system.

Other layers of the heart, such as the epicardium (the outermost layer) and the endocardium (the innermost layer), have different characteristics and functions. The epicardium provides a protective layer, while the endocardium lines the heart chambers and helps regulate blood flow. The heart's electrical conduction system, while important for coordinating heartbeats, is not the primary characteristic of the myocardium itself, which is fundamentally about muscle tissue and contraction.