Most of the skeletal structure of the human chest contour is made up of ribs, the uppermost rib being at the lower end of the clavicle and the lowermost one at the top of the internal posterior lumbar region. The rib cage connects the sternum to the anterior midline of the body toward the anterior thorax, from the first rib to the seventh rib, which is connected to both sides of the sternum, where the sternocostal joints are held in place by the rib cartilage and the lateral fibrocartilage. From the eighth rib to the tenth rib, the rib cartilage is connected to the previous rib cartilage, forming the rib arch as a whole, while the eleventh rib and the last twelfth rib, with their rib heads near the abdominal cavity, are in a free state. Below the clavicle and above the abdomen, as well as the entire posterior back, the axillae are the distribution areas of the ribs.