The Pericardium

Blood vessels and nerves of the heart | Main Anatomy Index | Manubriosternal plane

Last updated 30 March 2006

The Pericardium

• The pericardium (G. around the heart) is a double-walled fibroserous sac that encloses the heart (G. kardia) and the roots of the great vessels.
• It is located in the middle mediastinum, posterior to the body of the sternum and the 2nd to 6th costal cartilages, and anterior to T5 to T8 vertebrae.

• The pericardium consists of two parts: (1) a strong external layer composed of tough fibrous tissue, called the fibrous pericardium, and (2) an internal double-layered sac composed of a transparent membrane called the serous pericardium.

The Fibrous Pericardium

• The fibrous pericardium is the tough, more or less conical outer sac of pericardium, which protects the heart against sudden overfilling.
• Its truncated apex is pierced by the aorta, pulmonary trunk, and SVC.

• The ascending aorta carries the pericardium superiorly beyond the heart to the level of the sternal angle.
• The external surface of the fibrous pericardium has a dull appearance and its base rests on and is fused with the central tendon of the diaphragm.

• Anteriorly, the fibrous pericardium is attached to the posterior surface of the sternum by condensations of connective tissue called sternopericardial ligaments.
• The fibrous pericardium is also fused with the tunica adventitia of the great vessels.

• Thus, the fibrous pericardial sac is influenced by movements of the sternum, diaphragm and heart.

• The central tendon of the diaphragm and the pericardium are pierced by the IVC on the right side.

• The fibrous pericardium extends 1 to 1.5 cm to the right of the sternum and 5 to 7.5 cm to the left of the median plane at the level of the 5^th intercostal space.
• It is separated by the sternum and costal cartilages of the 2^nd to 6^th ribs by the lungs and pleura, except where it is attached to the posterior surface of the sternum by the sternopericardial ligaments and where the bulge of the heart intervenes.

The Serous Pericardium

• The serous pericardium consists of two layers: a parietal pericardium and a visceral pericardium.

• The parietal pericardium is fused to the internal surface of the fibrous pericardium and is so closely adherent to it that they are difficult to separate.

• The visceral pericardium is reflected onto the heart where it forms the epicardium, the external layer of the heart wall.

• The potential space between the parietal and visceral layers of the serous pericardium is called the pericardial cavity.
• It normally contains a thin film of serous fluid that enables the heart to move and beat in a frictionless environment.

• The visceral pericardium is reflected from the heart and great vessels to become continuous with the parietal pericardium. This is where the aorta and pulmonary trunk leave the heart and the superior and inferior venae cavae and pulmonary veins enter the heart.

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The Pericardial Sinuses

• The sinuses of the pericardium develop during folding of the embryonic heart, a process that produces reflections in the pericardium.

The Transverse Pericardial Sinus

• When the pericardial sac is opened anteriorly, a digit can be inserted into a recess posterior to the ascending aorta and pulmonary trunk, and anterior to the SVC.
• This recess is known as the transverse pericardial sinus.
• At its left and right ends, it communicates with the main part of the pericardial cavity.

The Oblique Pericardial Sinus

• As the pulmonary veins and IVC penetrate the fibrous pericardium to enter the heart, they bulge into the pericardial cavity.
• Consequently, they are partly covered by serous pericardium, which forms a somewhat inverted, U-shaped blind recess, called the oblique pericardial sinus.
• It is a wide, slit-like recess posterior to the heart that extends posterior to the left atrium.
• The thoracic part of the IVC is to the right of this sinus.

• The oblique pericardial sinus, which can be entered inferiorly, will admit several digits; however, they cannot pass around any of the vessels because this sinus is a blind sinus (cul-de-sac).

• There is a close relationship between the transverse and oblique pericardial sinuses. Only two layers of serous pericardium separate them.

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Arterial Supply of the Pericardium

• Its main arteries are the pericardiacophrenic and musculophrenic arteries, which are branches of the internal thoracic arteries.
• It also receives pericardial branches from the bronchial, oesophageal, and superior phrenic arteries.
• The epicardium is supplied by the coronary arteries.

Venous Drainage of the Pericardium

• Its veins are tributaries of the azygos systems of veins.
• Pericardiacophrenic veins also enter the internal thoracic veins.

Innervation of the Pericardium

• The nerves of the pericardium are derived from the vagus and phrenic nerves and the sympathetic trunks.

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