The mammary glands are located in the human chest, and behind the two mammary glands is the thorax, and the parts between the two mammary glands are, in order from front to back, the most anterior is the lateral rib cartilage and the sternum, which is located in front of each rib in the median line. In the intercostal space and between the ribs and the sternum there are many neurovascular distributions, and further medially there is the mediastinal cavity and the thoracic cavity on both sides, as well as the heart on the left side. In the mediastinal cavity, the esophagus, trachea, major blood vessels and lymphatic vessels pass up and down, among which the trachea is divided into left and right main bronchi to the left and right side of the chest cavity, and the esophagus is connected to the stomach at the lower cardia. Another important gland in the mediastinum is the thymus, and further back is the spine, which corresponds to the location of the thoracic vertebrae between the two breasts. Therefore, the area between the two breasts is basically the heart and lung organs and tissues, except for the esophagus of the digestive system.