Where are the four heart valves located, in relation to the heart's structures?

The heart valves are located within the endocardium, which is the innermost layer of the heart. This layer provides a smooth lining for the heart chambers and covers the heart valves. The endocardium is crucial for the proper functioning of the valves, as it allows for smooth blood flow and minimizes turbulence as blood moves through the heart.

The myocardium, which is the thick, muscular middle layer of the heart wall, plays a crucial role in contracting and pumping blood but does not house the valves themselves. The pericardium is the fibrous sac that encases the heart, providing protection and reducing friction during heartbeats, while the epicardium is the outermost layer of the heart wall. Thus, the endocardium is the specific layer that contains the heart valves, allowing them to effectively regulate blood flow between the heart chambers and into the arteries.