The main organs inside the left chest are the heart, left lung, diaphragm, and left bronchus. 1. Heart: Most of the heart is located in the left thoracic cavity, obliquely located in the middle mediastinum of the thoracic cavity. The heart is the power organ that maintains blood circulation, drives blood flow, and is also involved in endocrine functions. 2. Left lung: The left lung is located in the left side of the chest cavity. Its main function is gas exchange. 3. Diaphragm: located at the junction of the thoracic cavity and the abdominal cavity, it is a flat and thin muscle in the shape of a dome, and there is the left half of the diaphragm in the left thoracic cavity. 4. Left bronchus: the left bronchus is thin and long, about 5cm in length and 1.5~2.0cm in diameter, making an angle of 40-45 degrees with the longitudinal axis of the trachea. The bronchus goes out in the sixth thoracic vertebrae and enters into the hilum, and it is divided into upper and lower lobe bronchus. If the position of the left chest is abnormal, it may be that the above organs have lesions, and prompt medical attention is recommended.