There are three layers that make up the heart muscle. They include: Epicardium, Myocardium and the Endocardium.
The Epicardium is the surface of the heart. Arteries and Veins lay travel through this layer and goes deep in the hearts layers to feed it Oxygen from the arteries and veins which carry Deoxygenated blood back into the R Atrium. There is also a layer of fat(adipose Tissue)running down the L ventricle which supplies energy(ATP)
The Myocardium is the layers of Muscle that contracts and squeezes the heart so blood can travel through the heart with force. The intercalated discs are specific in this layer which controls the calcium which is needed for contraction of the hearts and pressures in the ventricles. The Left side of the heart has greater pressure than the right.
The Endocardium is the innermost layer that structures the bloods direction(Cardiac cycle) and contains specific tissues structures necessary in the normal anatomy and workings of the blood travel.
There is also a pericardium which is a sac around the heart as a cover. This protects the surface of the heart.