What is the Pericardium?

The term pericardium is derived from the Greek prefix peri- (“around”) and kardia (“heart”), implying a structure that envelops or encloses the heart. Morphologically, the pericardium is a fluid filled sac-like structure that surrounds the heart.

Anatomic structure

The pericardium is a double-walled structure made up of an outer fibrous layer and an inner serous layer.

The fibrous layer of the pericardium is a single connective tissue layer that is made up of collagen (type I and type III mainly) and elastin fibers; it is elastic and yet non-distensible. This layer of the pericardium is held in position cranially by its membranous folds that are interdigitating with the tunica adventitia of the great vessels. It is also held caudally by ligaments that are connected to the central tendon of the diaphragm, ventrally to the sternum by superior and inferior pericardiosternal ligaments, and dorsally by ligaments fastening it to the esophagus and spine.

Comparatively, the serous layer of the pericardium is made up of an outer parietal layer and inner visceral layer, each of which is comprised of a single layer of epithelial cells. The parietal layer lines the inner regions of the fibrous pericardium, while the visceral layer lines the outer layer of the heart and is therefore also known as the epicardium.

Pericardium - Definition, Function & Layers - Human Anatomy | Kenhub

Pericardial cavity

A void space found among the two linings of the serous pericardium is called the pericardial cavity, which encircles the heart.

Between the parietal and visceral layer is the pleural cavity, which holds the pleural fluid. About 20–30 ml in volume, this serous fluid acts as a lubricant and minimizes friction between the epicardium and parietal layer as the heart muscles expand and contract with the beating of the heart. Thus, the pericardial cavity allows the heart movement to remain flexible.

The pericardial cavity surrounds the heart completely, except at the inlet and outlet of the cardiac vessels, where they form two significant tubes. One of the tubes serves as an interconnection to the inferior and superior vena cava, as well as the pulmonary veins, whereas the other connects the aorta and the pulmonary trunk.

Blood supply and innervation of the pericardium

Blood supply to the pericardium occurs mainly through the pericardiophrenic artery, although a few minor contributions also occur via the musculophrenic artery, esophageal artery, bronchial artery, and superior phrenic artery.

The coronary artery is also involved, but it supplies blood only to the visceral layer. Draining of blood from the pericardium involves the pericardiophrenic veins, as well as the azygos venous system.

The innervations of the outer fibrous and parietal pericardium are due to the phrenic nerve (C3-C5), and it also provides motor and sensory innervation to the diaphragm. This nerve originates from the neck and travels down through the thoracic cavity. The phrenic nerve is a general source of referred pain, as can be demonstrated in cases where shoulder pain arises as a result of pericarditis. Additionally, the visceral pericardium is also innervated by the vagus and sympathetic nerves.

Pericardial sinuses

In medical terminology, a sinus is a passage or channel. There are two sinuses in the pericardial cavity, which include the transverse pericardial sinus and the oblique pericardial sinus. Both of these sinuses are formed through embryonic folding of the heart tube during ontogeny.

The reflections or folds of the serosal layer result in the formation of a set of complex tubes, one enclosing the aorta and the pulmonary trunk, whereas the other encloses the superior and inferior vena cave and the pulmonary veins. This results in a transverse sinus across the pericardium that separates the arterial blood vessels and the venous blood vessels.

The index finger can pass through the transverse sinus, which helps surgeons to identify the blood vessels of the heart during coronary artery bypass surgery.

The oblique sinus is formed by the reflection of the pericardial membranes onto the pulmonary veins. It is bounded by the inferior vena cava and the right pulmonary veins on one side, as well as the left pulmonary veins on the other.

Functions of the pericardium

The pericardium is known to have some specific functions, including:

  • Tethering: The pericardium holds the heart in place within the cardiac cavity.
  • Limiting: The pericardium prevents overfilling of the ventricles and consequent overexpansion of the heart.
  • Lubrication: The pericardium lubricates the moving surfaces of the heart.
  • Protective: The pericardium is a physical barrier between the muscular heart and the surrounding organs (e.g. lung) that may be prone to infection.

The pericardium is also able to transmit intra-thoracic changes in pressure that occur with changes in respiration, as the pressure in this structure is 2–5 mm Hg lower than the normal pressure within the thoracic cavity.

Furthermore, the non-distensible nature of the pericardium provides an overall constraint on the total heart volume and prevents irregular expansion of the chambers.

Because of its enclosing anatomic structure, the pericardium ensures that the left and right ventricles are equally compliant. Moreover, as the overall volume is fixed and expansion of one chamber automatically impedes the expansion of another, thereby ensuring that the heart chambers work rhythmically and in unison.


Further Reading

Last Updated: Jan 16, 2023

Dr. Tomislav Meštrović

Written by

Dr. Tomislav Meštrović

Dr. Tomislav Meštrović is a medical doctor (MD) with a Ph.D. in biomedical and health sciences, specialist in the field of clinical microbiology, and an Assistant Professor at Croatia's youngest university - University North. In addition to his interest in clinical, research and lecturing activities, his immense passion for medical writing and scientific communication goes back to his student days. He enjoys contributing back to the community. In his spare time, Tomislav is a movie buff and an avid traveler.


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  1. Abby May Abby May United States says:

    What happens when the collagen/elastin within the pericardium begins to deplete with age? Does the pericardium begin to rub together creating pericarditis?

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