Sternum

The long, narrow, flat plate of bone at the front of the chest. The sternum has 3 parts: an upper, triangular portion (manubrium); a long middle part (body); and, at the lower end, a small, leaf-shaped projection (xiphoid process). The upper manubrium articulates with the inner ends of the clavicles. The ribs are attached to the sides of the manubrium and body by cartilage. Between the manubrium and body is a symphysis joint, allowing slight movement when the ribs rise and fall during breathing. Great force is required to fracture the sternum. The main danger of such an injury is the possibility that the broken bone may be driven inwards, damaging the heart, which lies behind the sternum.