The Pericardium

The pericardium is a fibro serous sac that encloses heart and blood vessels originating from the base of the heart. It is located in the middle mediastinum, posterior to the body of the sternum and the second to sixth costal cartilages and anterior to the fifth to eighth thoracic vertebrae. It serves as a lubricant container in which different parts of the heart can contract and restrict excessive movement of the heart. It has two main layers the fibrous and serous pericardium.

Fibrous pericardium

It is a thin elastic layer and the outermost layer of the pericardium which is firmly attached below to the central tendon of the diaphragm and in front to the sternum by the Sterno pericardial ligaments. It lines anterior section of the vertebral column of the thoracic wall posteriorly and pleural sac anteriorly.

Serous pericardium

It is situated next to the fibrous pericardium and dived into parietal and cervical serous pericardium. The parietal pericardium strains fibrous layer externally and contemplated around the roots of the great vessels to grown to be non-stop with the visceral layer of the serous pericardium. The inner layer of the serous pericardium covers the walls of coronary heart intently and is frequently referred to as the pericardium. 

There is a small slit like space between the parietal and visceral layer, containing fluid which serves as a lubricant and reduces friction during the heart beat. In normal condition, it contains nearly 50ml of fluid. On the posterior surface of the heart, the reflection of serous pericardium around the large veins forms a recess called oblique sinus and reflection around the aorta and pulmonary trunk forms a transverse sinus. 

Nerve Supply

The visceral layer of the serous pericardium is innervated by sympathetic nerve and the vagus nerves. The fibrous and parietal layer of the pericardium is innervated by phrenic nerves.

Pericarditis

In inflammation of the serous pericardium ( pericarditis ) pericardial fluid may accumulate excessively, which can compress the thin-walled atria and interfere with the filling of the heart during diastole. This compression of the heart is referred as cardiac tamponade, which can also occur secondary to the stab and gunshot wounds when the chambers of the heart have been penetrated.

Blood Supply and Venous Drainage

The fibrous and parietal pericardium is supplied with an internal thoracic artery, and descending thoracic aorta. Coronary arteries supply blood to the visceral serous pericardium. Azygos and internal thoracic vein drain venous blood from the fibrous and parietal pericardium. Visceral serous pericardium - drain into the coronary sinus.`