Which layer of the heart is known as the inner lining?

The inner lining of the heart is referred to as the endocardium. This layer is critical because it provides a smooth surface for blood to flow within the heart chambers and lines the heart valves. The endocardium is composed of a thin layer of endothelial cells, which helps to minimize friction as blood moves through the heart, reducing the risk of clot formation and ensuring efficient circulation.

In contrast, the myocardium is the thick, muscular middle layer responsible for the contraction and pumping action of the heart. The epicardium, which is the outer layer of the heart, serves as a protective layer and is also involved in the production of pericardial fluid, which helps reduce friction between the heart and surrounding structures. The pericardium, a fibrous sac surrounding the heart, provides additional protection and support. Understanding the structure and function of these layers is essential for comprehending how the heart operates and maintains circulation throughout the body.