What is the name of the thickest middle muscle layer of the heart?

The thickest middle muscle layer of the heart is known as the myocardium. This layer is primarily composed of cardiac muscle tissue, which allows the heart to contract and pump blood effectively throughout the body. The myocardium is responsible for the heart's ability to perform work, and its thickness varies according to the function each chamber has. For example, the left ventricle has a considerably thicker myocardium compared to the right ventricle, as it must generate more force to pump blood throughout the entire body, while the right ventricle only needs to pump blood to the lungs.

The endocardium, which is another layer of the heart, lines the inner chambers and is involved in providing a smooth surface to facilitate blood flow. The epicardium is the outer layer that protects the heart, and the pericardium is the fibrous sac that surrounds the heart, containing a lubricating fluid to reduce friction as the heart beats. Therefore, understanding the role and structure of each layer helps clarify why the myocardium is essential for cardiac function.