Walls of the Heart

The walls of the heart is the same in the atria and ventricles:

• Epicardium (visceral layer of serous pericardium) has a layer of mesothelial cells on the outer surface of the heart, including underlying connective tissue. It contains blood vessels and nerves (e.g. purkinje fibers) that supply the heart
• Myocardium is the cardiac muscle
• Endocardium is the innermost layer of the heart wall (and also lines the interatrial and interventricular septum and valves). It consists of:
• An inner layer with endothelial and subendothelial connective tissue
• A middle layer with dense connective tissue and smooth muscle cells
• A deep layer (also known as the subendocardial layer) with connective tissue and the conducting system (purkinje fibers). It is continuous with the myocardial connective tissue