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Not only do they act as an exit gate, but they also prevent backflow into the chamber. Valves are an important component of the heart. These fibers are the Purkinje fibers after they divide within the interventricular septum and branch into the ventricles.

As the fibers travel inferiorly, it penetrates the central fibrous body of the cardiac skeleton to form the bundle of His. These impulses travel throughout the atria until it reaches the atrioventricular (AV) node, located between the interatrial and interventricular septum. Electrical impulses initiate at the sinoatrial (SA) node, situated at the junction of the superior vena cava and right atrium. The impulse conducting system has specialized cardiac cells for the conduction of electrical impulses throughout the heart. The subendocardium is found between the endocardium and myocardium and contains the impulse-conducting system. The endocardium is composed of the endothelium and the subendothelial connective tissue layer. Coronary arteries and veins, lymphatic vessels, and nerves run below the epicardium.

The epicardium constitutes the visceral pericardium, underlying fibro-elastic connective tissue, and adipose tissue.

The two layers of the pericardium are called the outer fibrous/parietal pericardium and the inner serous/visceral pericardium. A double-layer, fluid-filled sac known as the pericardium surrounds the heart.

These three layers of the heart are embryologically equivalent to the three layers of blood vessels: tunica adventitia, tunica media, and tunica intima, respectively. The wall of the heart separates into the following layers: epicardium, myocardium, and endocardium. Functions of the fibrous skeleton include providing a strong framework for cardiomyocytes, anchoring the valvular leaflets, and acting as electrical insulation separating the conduction in the atria and ventricles. The base of the heart contains a highly dense structure known as the fibrous or cardiac skeleton. The fibrous skeleton, cardiac muscle, and impulse conduction system constitute the basic framework of the heart.