All 12 ribs articulate posteriorly with the 12 thoracic vertebrae of the spinal column. Anteriorly the 7 true ribs articulate with the sternum or breast bone via attachments referred to as costal cartilages. The cartilagenous connections allow some mobility in the rib cage, necessary for the lungs to exapand properly during inspriation. Beneath the 7 true ribs lie 5 false ribs. The first three false ribs articulate with the 7th true rib. They do not directly attach to the sternum. The lasttwo false ribs ribs - floating ribs do not have any anterior connections.