Heart Wall

What is the epicardium?

The epicardium is the outer layer of the wall of the heart. It is composed of connective tissue covered by epithelium. The epicardium is also known as the visceral pericardium.

Function:
Provides an outer protective layer for the heart.


What is the pericardium?

The pericardium is the fluid filled sac that surrounds the heart and the proximal ends of the aorta, vena cava, and the pulmonary artery.
Function of the PericardiumThe pericardium has several functions:
Keeps the heart contained in the chest cavity.
Prevents the heart from overexpanding when blood volume increases.
Limits heart motion.

Pericardial MembranesThe pericardium is divided into three layers:
Fibrous Pericardium -
the outer fibrous sac that covers the heart.
Parietal Pericardium -
lies between the visceral pericardium and the fibrous pericardium.
Visceral Pericardium -
also called the epicardium, this is the outer layer of the wall of the heart.
Pericardial CavityThe pericardial cavity lies between the visceral pericardium and the parietal pericardium. This cavity is filled with pericardial fluid which serves as a shock absorber by reducing friction between the pericardial membranes.
Pericardial DisordersPericarditis is a disorder of the pericardium in which the pericardium becomes swollen or inflamed. Some causes of pericarditis include bacterial or viral infections, cancer, and hear attack. Pericardial effusion is a disorder caused by the accumulation of large amounts of fluid in the pericardium.

Myocardium ;

What is the myocardium?

Myocardium is the muscular middle layer of the wall of the heart. It is composed of spontaneously contracting cardiac muscle fibers which allow the heart to contract.

Function:

Stimulates heart contractions to pump blood from the ventricles and relaxes the heart to allow the artria to receive blood.



What is the endocardium?

The endocardium is the inner layer of the heart. It consists of epithelial tissue and connective tissue.

Function:

Lines the inner cavities of the heart, covers heart valves and is continuous with the inner lining of blood vessels.
Purkinje fibers are located in the endocardium. They participate in the contraction of the heart muscle.