Written by the Fiveable Content Team • Last updated August 2025
Written by the Fiveable Content Team • Last updated August 2025
Definition
The epicardium is the outermost layer of the heart's wall, consisting of a thin layer of connective tissue and fat that serves as a protective layer. It plays a crucial role in lubricating the heart to prevent friction during its contractions.
This is the thick middle layer of the heart wall composed of cardiac muscle fibers responsible for contracting and forcing blood out of the heart chambers.
The innermost layer of the heart lining the chambers and valves, made up of a thin layer of endothelial cells that provides a smooth surface for blood to flow over with minimal resistance.
A double-walled sac containing the heart and the roots of great vessels that provides protection and limits excessive movement of the heart within the thorax