Answer:
PERICARDIUM MEMBRANE
The pericardium acts as mechanical protection for the heart and big vessels, and a lubrication to reduce friction between the heart and the surrounding structures. A very important role in all aspects of pericardial functions is played by mesothelial cells.
Our heart is surrounded by a double-layered membrane, called the pericardium or pericardial sac. This membrane keeps your heart in place in your chest cavity, restricts the expansion of your heart when your blood volume increases, and helps to protect your heart.
PERICARDIUM FLUID
Pericardial fluid is the serous fluid secreted by the serous layer of the pericardium into the pericardial cavity. ... This serous layer has two membranes which enclose the pericardial cavity into which is secreted the pericardial fluid.