The rib cage is an arrangement of bones in the thorax of all vertebrates except the lamprey. It is formed by the vertebral column, ribs, and sternum and encloses the heart and lungs. In humans, the rib cage, also known as the thoracic cage, is a bony and cartilaginous structure which surrounds the thoracic cavity and supports the pectoral girdle (shoulder girdle), forming a core portion of the human skeleton. A typical human rib cage consists of 24 ribs, the sternum (with xiphoid process), costal cartilages, and the 12 thoracic vertebrae. Together with the skin and associated fascia and muscles, the rib cage makes up the thoracic wall and provides attachments for the muscles of the neck, thorax, upper abdomen, and back.

Structure

Ribs are described based on their location and connection with the sternum. Ribs that articulate directly with the sternum are called true ribs, whereas those that connect indirectly via cartilage are termed false ribs.

Attachment

The terms true and false rib describe rib pairs that are directly or indirectly attached to the sternum. The phrase true rib (Latin: costae verae), or fixed rib, refers to the first seven, or vertebrosternal, rib pairs. The phrase false rib (Latin: costae spuriae), or vertebrochondral ribs refers to the eighth-to-twelfth pairs of ribs. The eighth-to-tenth pairs of ribs connect to the sternum indirectly via the costal cartilages of the ribs above them. Their elasticity allows ribcage movement for respiratory activity.