Final answer:
The visceral pericardium, also known as the epicardium, is the layer that directly covers the heart and helps reduce friction through the secretion of serous fluid in the pericardial cavity.
Step-by-step explanation:
Another name for the visceral pericardium is the epicardium. This is the inner layer of the serous pericardium that directly covers the heart's surface. The epicardium is a part of the pericardial sac, which is a membrane that serves to separate the heart from other mediastinal structures. This serous membrane forms the outermost layer of the heart wall and is essential for providing a lubricated surface, facilitating minimal friction during the heart's contractions.
The epicardium consists of a mesothelium, which is a type of simple squamous epithelium, supported by areolar connective tissue. The mesothelium is responsible for secreting the serous fluid that fills the pericardial cavity between the epicardium and the parietal layer of the serous pericardium, thereby reducing friction. Understanding the structure and function of the pericardial sac helps in grasping how the heart operates within the thoracic cavity.