The bones under the left breast are called ribs. There are 12 pairs of ribs in the human body, 12 on the left and 12 on the right, the back end is connected to the thoracic vertebrae, the first 1-7 ribs are connected to the sternum through the costal cartilage, which is called the true ribs, and the 8th-10th ribs are connected to the upper rib through the costal cartilage to form the arch of the ribs, as the 8th-10th ribs are not directly connected to the sternum, which is called the false ribs, and the 11th and 12th ribs are free from the front end, which is called the floating ribs, which together form the thorax, and play a role in support and protection. Ribs are small, curved bones, one end of which is attached to the side of the vertebrae, and the other end is free or attached to the sternum in the center of the chest, which is used to protect the lungs, heart, liver, esophagus and other organs. The sternal handle is flat to the 2nd rib, the thoracic nipple is flat to the 4th rib, the lower boundary of the lung is flat to the 6th, 8th and 10th ribs in the anterior axillary line, the mid-axillary line and the posterior axillary line, respectively. Pneumothorax puncture is often located in the mid-clavicular line between the 2nd ribs, and pleural effusion puncture is often located in the scapular line between the 7th ribs, and ribs do not only have a role in protecting the internal organs, but also have the function of localization. If there are uncomfortable symptoms in the left lower chest bone, consult the doctor in time.