The epicardium is the outermost layer of the heart wall, serving as a protective covering for the heart. It is a thin layer of tissue that consists of connective tissue and fat, providing cushioning and support. The epicardium also contains blood vessels and nerves that supply the heart. This layer is part of the pericardium, which is a double-walled sac surrounding the heart. The epicardium plays a role in the heart's function by facilitating the movement of the heart during contractions and helping to reduce friction between the heart and surrounding structures.