Sternum. The sternum, or breastbone, is a flat bone at the front center of the chest. The ribs and sternum make up what is called the ribcage.. The ribcage protects the lungs, blood vessels, and heart, along with parts of the spleen, stomach, and kidneys from traumatic injury. The sternum is attached to the first seven ribs and also to the clavicle, or collarbone. The sternum is made up of three parts called the manubrim, the body, and the xiphoid process. In adults, the sternum portions are fused. The top of the sternum is the manubrim, or handle.