The epicardium is the outermost layer of the heart wall, serving as a protective covering for the heart. It is composed of connective tissue and fat, which helps to cushion the heart and reduce friction as it beats. The epicardium also contains blood vessels and nerves that supply the heart. In addition to its protective role, the epicardium plays a part in the heart's function by producing a lubricating fluid that allows smooth movement between the heart and surrounding structures. This layer is essential for maintaining the overall health and efficiency of the heart, which is crucial for the proper functioning of the circulatory system.