pericardial fluid
Yes, it is.
The pericardium surrounds the heart like a protective sac. It contains fluid that decreases friction.
The pericardium. It is composed of two layers: the fibrous pericardium (the outer layer that is made of tough connective tissue) and the serous pericardium (the inner layer in which serous fluid provides lubrication for the heart to beat with almost no friction).
There are three layers to the pericardium. They go in alphabetical order. The first layer is the Fibrous Pericardium. The second layer is the parietal pericardium and the third and innermost layer is the visceral layer.
The membrane surrounding the heart is called the pericardium. It is a fluid sac that serves several purposes. One of the purposes of the pericardium is it contains the heart in the chest cavity. The pericardium also prevents the heart from overexpanding when the blood volume in the heart increases.
Fibrous pericardium and serous pericardium. The serous pericardium is made up of an outer parietal layer that is fused to the fibrous pericardium and an inner visceral layer (aka epicardium) that is a layer of the heart wall and adheres tightly to the heart.
Epicardium or inner layer of serous pericardium is the innermost layer of pericardium.
The heart is encased in two protective layers. The outer layer -- the pericardium -- covers the heart. It folds in on itself at the aorta forming the epicardium of the heart. Between these layers is a small amount of fluid (10-50 ml) that affords the layers a non-stick surface.
Parietal Pericardium
Because every organ has 2 layers of tissue and fluid to prevent friction the inner layer I believe is visceral and the outside is parietal. such as the visceral pericardium and parietal pericardium protect the heart.
Surrounding the heart is a fibrous sac called the pericardium. This sac protects the heart, and is actually composed of two layers: an inner visceral one and an outer parietal one. When the heart moves (i.e. when the heart beats), these two layers move with it. For this to happen, it is important that there is no friction between the two layers of the pericardium, which is why pericardial fluid lines the inner space between the them. Much like oil in an engine, the pericardial fluid makes for less friction between the inner and outer layer of the pericardium.
The fibrous pericardia is the most superficial layer. The serous pericardia is deeper than the fibrous pericardia.