The inner lining of the pericardial cavity is the pericardium, whereas the outer part of the heart wall is called the epicardium or the pericardium.

The inner lining of the pericardial cavity is the serous pericardium and the outer part of the heart wall is called the epicardium or the fibrous pericardium.

Explanation:

Heart is a mesodermally derived organ and it is situated in the thoracic cavity in between the two lungs slightly tilted to the left lung.

The pericardium is the membrane that surrounds and the main function is to protect the heart.

It consists of outer fibrous pericardium which is composed of tough,inelastic,dense and irregular connective tisssue and an inner serous pericardium froms a double layer around the heart.

Between the pareital and visceral layers of the serous pericardium is the pericardial cavity,a potential space filled with a few milliliters of pericardial fluid that reduces friction between the two members.