Is Visceral Pericardium and Epicardium same structure? What is the difference between visceral pericardium and epicardium? In this video Dr. Aizaz from MedicoVisual explains the interesting reason behind why visceral pericardium is called epicardium.
The epicardium is also called visceral pericardium. So both are the names of same structure.
Why is visceral pericardium of heart called epicardium?
Its reason is interesting.
Like many other organs, the developing heart is also surrounded by the intra-embryonic splanchnopleuric mesoderm. In other organs this intra-embryonic splanchnopleuric layer forms the visceral layer of peritoneum/pleura and the intra-embryonic somatopleuric mesoderm forms the parietal layer of peritoneum/pleura.
However, in case of heart, this intra-embryonic splanchnopleuric mesoderm aggregates and form a pro-epicardial organ, while rest of it degenerates. So, original layer is destroyed. But the pro-epicardial organ forms a new outer-most layer of the heart which is structurally very similar to the visceral layer. But is formed in a slightly different way. This newly formed mesothelial layer that is not formed directly by the intra-embryonic splanchnopleuric mesoderm, but instead secondarily formed by the pro-epicardial organ is more appropriately termed as "Epicardium".
In summary, the visceral layer of the pericardium is called the epicardium because it is derived from the pro-epicardial organ and not directly from the intra-embryonic splanchnopleuric mesoderm like the visceral layer of other organs. Even though it is structurally similar to the visceral layer, it is formed in a slightly different way, which warrants a different name.