What part of the heart wall is also a component of the pericardium?

The epicardium is the outer layer of the heart wall and serves a dual role as part of the pericardium. It is made up of a thin layer of connective tissue and is also known as the visceral layer of the serous pericardium. This layer adheres closely to the heart itself, providing protection and helping to anchor the heart within the chest cavity. It plays a vital role in allowing the heart to function smoothly by reducing friction as the heart beats.

In contrast, the endocardium, which lines the interior of the heart chambers, and the myocardium, which is the thick muscular layer responsible for contracting and pumping blood, do not have a structural or functional relationship with the pericardium. The pericardial sac is the fibrous outer layer that encloses the heart and is not part of the heart wall itself but rather a separate structure that protects and lubricates the heart. Therefore, the epicardium stands out as the correct answer because it directly forms part of the pericardium while also being a vital component of the heart's anatomy.