perikardium

The pericardium is a double-walled sac that surrounds the heart and the proximal portions of the great vessels. It consists of an outer fibrous pericardium and a double layer of serous pericardium—the parietal layer lining the fibrous sac and the visceral layer, or epicardium, covering the heart itself. The serous layers enclose a potential space, the pericardial cavity, normally containing a small amount of lubricating fluid.

Functions include anchoring the heart within the mediastinum, protecting it from infection and trauma, and limiting excessive dilation during diastole. The fibrous pericardium is relatively tough, helping to maintain position of the heart. Innervation is mainly via the phrenic nerves (C3–C5), which mediate pain referral to the shoulder; autonomic fibers reach the heart but the pericardium is sensitive primarily to mechanical stimuli. Blood supply to the pericardium comes from branches of the internal thoracic and phrenic arteries, and venous drainage mainly via the pericardiophrenic veins to the internal thoracic system.

Anatomically, the pericardial cavity contains recesses such as the transverse and oblique sinuses, identifiable during imaging or surgery. The pericardium can be involved in several clinical conditions, including pericarditis (inflammation), pericardial effusion (fluid accumulation), and cardiac tamponade (compression of the heart by fluid), as well as constrictive pericarditis where the fibrous sac becomes thickened. Diagnosis commonly uses echocardiography, with CT or MRI as adjuncts. Treatments range from anti-inflammatory therapy for mild pericarditis to pericardiocentesis for effusions and pericardiectomy for constrictive disease.