ANSWER -
The structure covering the upper portion of the heart is called the pericardium. The pericardium is a sac-like structure that surrounds the heart and protects it from external injury. It consists of two layers: an outer fibrous layer and an inner serous layer. The serous layer secretes a small amount of fluid that acts as a lubricant, allowing the heart to move freely within the pericardium. The pericardium is an important part of the heart's anatomy, as it helps maintain the proper functioning of the heart and protects it from injury or infection.