Which term refers to the muscle layer of the heart?

The term that refers to the muscle layer of the heart is myocardium. The myocardium is the thick, muscular middle layer of the heart, responsible for the contractions that pump blood throughout the body. Its structure consists of cardiac muscle, which is unique to the heart, allowing it to contract effectively and maintain the heartbeat. This muscular layer is crucial for the heart's function, as it enables the heart to pump efficiently and respond to various physiological demands.

In contrast, the epicardium is the outer layer of the heart that also serves as the inner layer of the pericardium, and it plays a protective role. The endocardium lines the heart's chambers and valves, helping to prevent blood from sticking to the heart's interior. The pericardium is a double-walled sac that surrounds the heart and provides cushioning and support, helping to protect the heart from trauma and infections. Understanding these layers is essential for appreciating how the heart functions as a vital organ in the circulatory system.