What type of pericardium has a double layer and reduces friction?

The serous pericardium is characterized by its double-layer structure, consisting of an inner visceral layer that adheres closely to the heart and an outer parietal layer that lines the fibrous pericardium. This arrangement allows the layers to create a pericardial cavity filled with pericardial fluid, which serves to reduce friction between the heart and surrounding structures during the heart's movements. The serous fluid acts as a lubricant, facilitating smooth heart contractions and preventing irritation from friction, which is particularly important given the heart's constant motion.

In contrast, options such as the fibrous pericardium primarily provide structural support and protection but do not have layers designed for friction reduction. Additionally, the terms like "aerolar pericardium" and "simple squamous pericardium" do not represent recognized components of the pericardial structure and thus are not relevant to the context of this question. The serous pericardium's unique design and fluid content are what make it crucial for the heart's efficient and pain-free functioning.