The middle part of the chest is the middle part of the inner side of the pleural cavity on both sides. It contains organs and organs that are connected by connective tissue and are adjacent to each other, and is called the mediastinum because it is not wrapped by the pleura or other tissues. The mediastinum contains mainly thymus, pericardium, heart, trachea, left and right main bronchi, esophagus, large intra-thoracic vessels, nerves, thoracic duct, lymph nodes and lymphatic vessels. The thymus gland tissue exists at an early age and gradually degenerates with age, and the mediastinum is fronted by the sternum and followed by the thoracic vertebral tissue.