What Is the Fibrous Pericardium?

The body relies on blood to sustain life. Blood is responsible for supplying the entire body with sustenance, in the form of nutrients and oxygen. It also contributes to the removal of waste products, such as carbon dioxide and various toxins. The heart, an involuntary muscle that cannot be consciously contracted or relaxed, is the center of the system responsible for distributing blood throughout the body. Fibrous pericardium is one part of a two-layered protective covering surrounding the heart.

The pericardium is the term used to describe the dual pouch-like casing that encloses the heart muscle and some essential blood vessels crucial to proper functioning of the heart such as the aorta, pulmonary arteries and veins, and the vena cavae, also referred to as the great vessels. This thin, stretchy yet durable covering is made up of a combination of dense and loosely packed connective tissue, cells that create a strong yet flexible double wrapping. The heart’s defensive sheath consists of the fibrous pericardium layer, the most superficial layer of the heart’s casing, and the serous pericardium layer, a double thick shell which is fused or united to the fibrous pericardium.

In addition to protecting the heart, the fibrous pericardium acts as an anchoring system that attaches to the surrounding areas keeping the heart in position. For example, this layer is fastened to the diaphragm, the primary breathing muscle, a sheet-like muscle that extends across the bottom of the rib cage. The pericardium also acts as a lubricating system with an area between the layers filled with a serous or fluid-like material called the pericardial cavity. This small space prevents friction that could irritate or inflame the heart or its covering.

Another important function of this casing is preventing the heart from overfilling with blood or over expanding in size. Though fibrous pericardium is somewhat flexible allowing the heart muscle to contract and relax, a movement that continuously changes its size, this casing does not allow the heart muscle to expand beyond its acceptable limits for normal functioning. However, when the heart excessively pushes against the pericardium or when there is a change in the fluid levels between the layers, the protective sac can become inflamed and irritated, a condition known as pericarditis. Pericarditis can result in symptoms ranging from chest pain and shortness of breath to leg swelling and general fatigue. A chronic swelling may interfere with the heart’s ability to function properly, thus decreasing the amount of blood that is traveling throughout the body.