Thoracic Cage (Rib Cage)

The thoracic cage, commonly called the rib cage, is the bony enclosure of the chest. It is built from 12 pairs of ribs and their costal cartilages, the sternum (breastbone) in front, and the 12 thoracic vertebrae behind. Together these structures form a protective, expandable cage around the vital organs of the thorax.

Ribs and Their Attachments

Each rib curves from the back to the front of the chest. Posteriorly, every rib articulates with the thoracic vertebrae at the costovertebral joints. Anteriorly, the ribs are classified by how they connect to the sternum:

• True ribs (1–7): connect directly to the sternum through their own costal cartilage.
• False ribs (8–10): connect indirectly, their cartilage joining the cartilage of the rib above.
• Floating ribs (11–12): do not reach the sternum at all and end within the back muscles.

This arrangement combines firm protection with flexibility, allowing the cage to expand and contract.

The Sternum

The sternum is a flat bone in the center of the front chest wall with three parts: the manubrium at the top, the body in the middle, and the small xiphoid process at the bottom. The clavicles (collarbones) attach to the manubrium, and the costal cartilages of the true ribs attach along its edges. The junction between the manubrium and body, the sternal angle, is an important landmark that lines up with the second rib.

Functions and Clinical Relevance

The rib cage protects the heart, lungs, and major blood vessels, and it provides attachment points for muscles of the chest, back, shoulder, and abdomen. Crucially, it enables breathing: when the muscles between the ribs and the diaphragm contract, the cage lifts and widens, drawing air into the lungs, then relaxes to push air out.

Clinically, rib fractures are common after chest trauma and can be painful because the cage moves with every breath. The xiphoid process and sternal angle guide procedures such as CPR hand placement. This information is educational and not medical advice.