The thoracic cage is a bony and cartilaginous structure which surrounds the thoracic cavity and supports the pectoral (shoulder) girdle. It consists of the 12 pairs of ribs, sternum, costal cartilages, and the 12 thoracic vertebrae. It, along with the skin and associated fascia and muscles, make up the thoracic (chest) wall.
The thoracic cage provides attachments for the muscles of the neck, thorax, upper abdomen, and back.
Clinically Oriented Anatomy, 4th ed. Moore, Keith L. and Arthur Dalley.