Bone · Chest

Ribs

Costae

The ribs are twelve pairs of curved, flattened bones that make the wall of the chest. Every one joins the thoracic spine behind; the upper seven reach the sternum in front through their own cartilage, the next three join onto the cartilage above them, and the last two end free in the muscle of the flank. They shield the heart and lungs, but they are not a cage in the rigid sense — they swing up and out on every inhale like bucket handles. The intercostals fill the gaps between them, the diaphragm attaches around their inner lower border, and the serratus anterior grips their outer surfaces from the shoulder blade.