The layer of membranes surrounding the heart is named pericardium. The heart is covered by a layer of epithelial cell membrane called pericardium( peri: around, cardium: heart Greek ). This membrane actually folds onto itself and forms 2 layers. The one on the hear is called the visceral pericardium and the one on the outer part is known as the parietal pericardium. There is some amount of fluid present between these layers which help for smooth movement during the movement of the heart( which moves a lot). This fluid is known as the pericardial fluid. Image: wikipedia.org
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