Pericardium

Pericardium is a thin, conical, fibroelastic sac or a membrane surrounding hearts and its great vessels.
Various functions of pericardium include preventing dislocation of heart by maintaining its original position, providing mechanical support to the heart and its great vessels and act as a lubrication, to lessen friction between the heart and the neighboring structures.
Gross anatomy.
Anatomically It has two main parts fibrous pericardium and serous pericardium.
Histology.
Histologically, pericardium consists of three layers: the serosa, the fibrosa, and an outer layer of epipericardial connective tissue.
Pericardial fluid is present in between these two layers.
The parietal pericardium (thickness 0.8–1 mm) consists of an outer fibrous connective tissue sac lined by serosa. The serosa comprises unilayer mesothelium (which is responsible for the formation and reabsorption of pericardial fluid) . It is surrounded by variable amount of fatty tissues, particularly in the cardiophrenic angles.
The pericardial sac consists of two pericardial sinuses namely oblique sinus and transverse sinus.
Clinical anatomy.
Pericardial effusion is clinical conditions characterized by excessive pericardial fluids in between the parietal and visceral layers. Pericardiocentesis is a clinical procedure carried out to remove excessive fluid that has built up in a pericardium. The inflammation of pericardium is called pericarditis.