What is the outer layer of the heart called?

The outer layer of the heart is known as the epicardium. This layer serves as a protective covering of the heart and is composed of connective tissue and epithelium, playing an important role in preventing friction between the heart and surrounding structures as the heart beats. The epicardium also contains coronary blood vessels that supply blood to the heart itself.

In contrast, the myocardium refers to the muscular middle layer of the heart, responsible for the contraction and pumping action of the heart. The endocardium is the innermost layer that lines the heart chambers and covers the heart valves, facilitating smooth blood flow within the heart. The pericardium, which is a fibrous sac surrounding the heart, provides additional protection and helps anchor the heart within the chest cavity, but it is not a layer of the heart itself. The distinction among these layers is important for understanding both heart anatomy and function.