The pericardium is the fluid filled sac that surrounds the heart and the proximal ends of the aorta, vena cava, and the pulmonary artery.

The pericardium has several functions. It keeps the heart contained in the chest cavity. The pericardium also prevents the heart from overexpanding when blood volume increases.

Within the pericardium lies the pericardial cavity. This cavity is filled with pericardial fluid which reduces friction between the pericardial membranes.

Learn more about the aorta and the heart, see:

• Anatomy of the Heart
  
• Cardiovascular System Quiz