- Pericardium - The Pericardium limits the heart's motion, protects it from infection from other organs, and lubricates the heart.
- Epicardium - Layer of the pericardium that is closely aligned to the heart wall.
- Myocardium - The myocardium 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.
- Endocardium - a white sheet of endothelium resting on a thin connective tissue layer. Purkinje fibers are located in the endocardium. They participate in the contraction of the heart muscle.
Along with the four main layers of the heart, there are also multiple layers of the pericardium. They include the Visceral pericardium, percardial cavity, fibrous pericardium, and the parietal pericardium.
- The fibrous pericardium is the outermost layer of the pericardium. It's main purpose is to protect the heart, anchoring it to the surrounding walls, and preventing it from overfilling with blood.
- The Parietal pericardium is the secondmost layer of the skin. The main job that the parietal has is to separate the visceral pericardium from the fibrous pericardium.
- In between the Parietal pericardium and the Visceral pericardium is the pericardial cavity. This cavity is filled with pericardial fluid which serves as a shock absorber by reducing friction between the pericardial membranes.
- Finally the last and innermost layer of the pericardium is the visceral pericardium. Also called the epicardium, this layer separates the myocardium from the serous pericardium.