Full Bones of the Chest and Upper Back Description
[Continued from above] . . . and make up a cage to protect the heart, lungs and other upper organs. The twelve pairs of ribs join at the back with the twelve thoracic vertebrae. Seven true ribs attach to the sternum, or breastbone, which is a long, narrow, flat plate that forms the center of the front of the chest. It also joins the clavicles (shoulder blades) on its upper border. The sternum is very strong and requires great force to fracture. It's built to protect the heart, which lies behind it. The remaining five pairs of ribs are called false ribs because their cartilages do not reach the sternum directly. Instead, the cartilages of the upper three false ribs join the cartilages attached to the ribs above, while the last rib pairs have no cartilaginous attachments to the sternum at all. These last two pairs are sometimes called floating ribs.
Some of the body's most significant organs are protected by the skeletal system of the upper abdomen.