Which of the following tissues lines the interior surfaces of the heart?

The epicardium is the outermost layer of the heart wall, serving as a protective layer that also contains blood vessels and nerves. While it is an important component of the heart's structure, it does not line the interior surfaces, which is specifically the role of the endocardium.

The myocardium is the thick, muscular middle layer of the heart responsible for contracting and pumping blood throughout the body. Although it is essential for heart function, it does not line any surfaces; rather, it forms the bulk of the heart's structure, distinguishing it from the endocardium, which specifically lines the chambers.

The pericardium is a double-layered sac that surrounds the heart, providing protection and anchoring the heart within the thoracic cavity. While it plays a significant protective role, it does not line the heart's interior surfaces, which is exclusively the function of the endocardium.