Epicardium (external layer)
the thin, transparent outlayer pf the heart wall, it is also called the visceral layer of the serous pericardium. It is composed of mesothelium and delicate connective tissue that imparts a smooth, slippery texture to the outermost surface of the heart.

Function:
*Protects the heart
*Provides signals for embryonic heart formation and maturation
*Secretes factors for cardiomyocyte proliferation and survival
*Helps with the heart’s injury response and regeneration

Myocardium (middle layer)
It is a cardiac muscle tissue, makes up about 95% of the heart and is responsible for its pumping action. Although it is striated like skeletal muscle, cardiac muscle is involuntary like smooth muscle.

Function:
It stimulates heart contractions to pump blood from the ventricles and relaxes the heart to allow the atria to receive blood. These contractions produce what is known as a heart beat. The beating of the heart drives the cardiac cycle which pumps blood to cells and tissues of the body.

Endocardium (inner layer)
It is a thim layer of endothelium overlying a thin layer of connective tissue. It provides a smooth lining for the chambers of the heart and covers the valves of the heart. The endocardium is continuous with the endothelium lining of the large blood vessels attached to the heart, and it minimizes surface friction as blood passes through the heart and blood vessels.

Function:
Endocardium keeps the blood flowing through the heart separate from the myocardium, or cardiac muscles. It also lines the valves, which open and close to regulate blood flow through the chambers of the heart.