The endocardium is a thin layer of tissue that lines the interior of the heart chambers. It is composed of endothelial cells and connective tissue, providing a smooth surface that helps blood flow easily through the heart. This layer also plays a role in regulating heart function and protecting the heart from infections. In addition to lining the chambers, the endocardium is involved in the formation of heart valves. These valves ensure that blood flows in the correct direction, preventing backflow. Any damage or inflammation to the endocardium can lead to conditions such as endocarditis, which can affect overall heart health.