Pericardial sac

Pericardium
Walls of the heart, showing pericardium at right.
Posterior wall of the pericardial sac, showing the lines of reflection of the serous pericardium on the great vessels
Details
Artery	Pericardiacophrenic artery
Nerve	Phrenic nerve
Identifiers
Latin	Pericardium
Greek	περίκάρδιον
MeSH	A07.541.795
TA	A12.1.08.001
FMA	9869
Anatomical terminology []

The pericardium (from the Greek περί, "around" and κάρδιον, "heart") is a double-walled sac containing the heart and the roots of the great vessels. The pericardial sac has two layers, a serous layer and a fibrous layer. It encloses the pericardial cavity which contains pericardial fluid.

The pericardium fixes the heart to the mediastinum, gives protection against infection, and provides the lubrication for the heart.

The pericardium is a tough double layered fibroserous sac which covers the heart. The space between the two layers of serous pericardium (see below), the pericardial cavity, is filled with serous fluid which protects the heart from any kind of external jerk or shock. There are two layers to the pericardial sac: the outermost fibrous pericardium and the inner serous pericardium.

The fibrous pericardium is the most superficial layer of the pericardium. It is made up of dense and loose connective tissue, which acts to protect the heart, anchoring it to the surrounding walls, and preventing it from overfilling with blood. It is continuous with the outer adventitial layer of the neighboring great blood vessels.

The serous pericardium, in turn, is divided into two layers, the parietal pericardium, which is fused to and inseparable from the fibrous pericardium, and the visceral pericardium, which is part of the epicardium. Both of these layers function in lubricating the heart to prevent friction during heart activity.

The visceral layer extends to the beginning of the great vessels (the large blood vessels serving the heart) becoming one with the parietal layer of the serous pericardium. This happens at two areas: where the aorta and pulmonary trunk leave the heart and where the superior vena cava, inferior vena cava and pulmonary veins enter the heart.

In between the parietal and visceral pericardial layers there is a potential space called the pericardial cavity, which contains a supply of lubricating serous fluid known as the pericardial fluid.