Human Thorax (Chest)
Thorax. The thorax, or chest, is an elongated conical-shaped cage, formed by the sternum and costal cartilages in front, the 12 ribs on each side, and the bodies of the 12 dorsal vertebrae behind. It contains and protects the principal organs of respiration and circulation. Labels: 1 to 12, ribs; d, d, costal cartilages; e, upper end of sternum; b, middle portion of sternum; 1 a, first dorsal vertebra; 12 a, twelfth dorsal vertebra; 7 a, seventh cervical vertebra; 1 to 7, true ribs; 8 to 12, false ribs; 11, 12, floating ribs. 10th rib is defective; it should be attached to the costal cartilage.