Both men and women have 24 ribs, twelve on each side. Each rib is attached to a spinal bone (thoracic vertebra) in the back. The first seven pairs of ribs join the breastbone (sternum) in the center of the chest. The front ends of the eighth, ninth, and 10th pairs are connected to the ribs above them. The 11th and 12th pairs are called floating ribs, because they are anchored in place only by connective tissue.

One in every few hundred people have an extra rib. These are called cervical ribs, because they arise from one of the spinal bones in the neck (cervical vertebrae).