Anatomy of the Heart: Pericardium

Pericardium
Pericardium is the membranous sac that surrounds the heart. Credit: DEA PICTURE LIBRARY/Getty Images

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. Together, the heart and circulatory system form the cardiovascular system. The primary function of the heart is to help circulate blood to the tissues and organs of the body.

Function of the Pericardium

The pericardium has several functions:

  • Keeps the heart contained in the chest cavity.
  • Prevents the heart from over-expanding when blood volume increases.
  • Limits heart motion.

Pericardial Membranes

The pericardium is divided into three membrane layers:

  • Fibrous Pericardium - the outer fibrous sac that covers the heart. It provides an outer protective layer that is attached to the sternum by sternopericardial ligaments. Fibrous pericardium helps to keep the heart contained within the chest cavity. It also protects the heart from infection that could potentially spread from nearby organs such as the lungs.
  • Parietal Pericardium - layer between the fibrous pericardium and visceral pericardium. It is continuous with fibrous pericardium and provides an additional layer of insulation for the heart.
  • Visceral Pericardium - this inner layer of the pericardium also forms the epicardium, or outer layer of the wall of the heart. It protects the inner heart layers and also assists in the production of pericardial fluid.

    Pericardial Cavity

    The 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. There are two pericardial sinuses that pass through the pericardial cavity.

    A sinus is a passage way or channel. The transverse pericardial sinus is positioned above the left atrium of the heart, anterior to the superior vena cava and posterior to the pulmonary trunk and ascending aorta. The oblique pericardial sinus is situated posteriorly to the heart and is bounded by the inferior vena cava and pulmonary veins.

    Pericardial Disorders

    Pericarditis is a disorder of the pericardium in which the pericardium becomes swollen or inflamed. This inflammation disrupts normal heart function. Pericarditis can be acute (happens suddenly and over quickly) or chronic (happens over a period of time and lasts for a long time). Some causes of pericarditis include bacterial or viral infections, cancer, kidney failure, certain medicines, and heart attack.

    Pericardial effusion is a condition caused by the accumulation of large amounts of fluid between the pericardium and the heart. This condition can be caused by a number of other conditions that affect the pericardium, such as pericarditis.

    Cardiac tamponade is pressure build up on the heart due to excessive fluid or blood build up in the pericardium. This excess pressure does not allow heart ventricles to fully expand. As a result, cardiac output is lowered and blood supply to the body is insufficient.

    This condition is most commonly caused by hemorrhage due to penetration of the pericardium. The pericardium may become damaged as a result of severe trauma to the chest, a knife or gunshot wound, or accidental puncture during a surgical procedure. Other possible causes of cardiac tamponade include cancer, heart attack, pericarditis, radiation therapy, kidney failure, and lupus.