In the thoracic cavity, the pleura is subdivided, forming the pleural cavity and the cavity.

perciardial

Explanation:

The pericardium is a fibroserose sac that completely envelops the heart, in the form of a bag or sac, of great consistency, with a series of extensions that cover the root of the great vessels. It consists of two layers, a visceral (also called an epicardium) tightly attached to the surface of the heart, and a parietal separated from the anterior by a narrow capillary space that contains the pericardial fluid. The visceral pericardium is formed by a layer of mesothelial cells, adhered to the epicardial fat and epicardium and, on the other hand, in contact with the pericardial fluid. The parietal pericardium is a more fibrous layer, formed internally by mesothelial cells in continuity with those of the epicardium, but it also has another fibrous outer layer formed by layers of collagenous fibrils arranged in different directions within a connective tissue matrix that also contains elastin fibrils

The pericardial sac on the parietal part is connected by fibrous connections to the central tendon of the diaphragm and, inferior to the diaphragm by the phrenic-pericardial ligament. It is also linked by superior and inferior ligaments to the sternum (sternopericardial ligaments). On the back, the pericardium is in intimate relationship with the esophagus and descending aorta. Laterally it is related to the pleura, phrenic nerves and vessels. In its anterior part, the parietal pericardium is in intimate contact with the left half of the lower part of the sternum and, sometimes, with the fourth and fifth left sterile cartilages. On its back, the parietal pericardium maintains fibrous connections with the spine .

don't worry, but do consult a doctor.

explanation:

having a high metabolism at age 13 is not abnormal.   however, if you are concerned, do consult a doctor.   the doctor may identify a correctable issue, and then you'll have your answer.   in the meantime, there are a few steps you might consider.

first, reflect on just how much physical activity (work out and dancing) you are getting relative to your caloric intake.   keep in mind that if you are interested in gaining weight, you must have a higher caloric intake than output.   second, if eating robust healthy meals is not providing enough calories, you'll need to include high caloric, yet healthy, snacks.   i warn against using an over the counter high-calorie supplement (drink or food) until you have consulted a doctor.