Figure 1-7
Right, lateral view of the ribs of the thorax classified according to their anterior attachments.

Figure 1-8
Seventh rib, posterior view.

Figure 1-9
Parts of the Sternum.

The twelve ribs articulate posteriorly with twelve thoracic vertebrae on each side of the thorax. The first seven ribs attach anteriorly to the sternum and are called true or vertebrosternal ribs. The remaining five are false ribs; of these, the first three are called vertebrochondral ribs and the last two are called floating or vertebral ribs. (Figure 1-7)

A typical rib is composed of a wedge shaped head with a large inferior facet for articulation with its vertebra and a small superior facet for articulation with the vertebra above. The head is connected to the shaft or body of the rib by a short neck. The neck extends from the head to a tubercle that articulates with the transverse process of the rib's vertebra.

The shaft of the rib curves from the neck to the costal cartilage attachment on the anterior thorax. Along the inferior border, is a groove called the costal groove that accommodates the intercostal vein, artery and nerve. (Figure 1-8)

The sternum is an elongated flattened bone forming the middle portion of the anterior wall of the thorax. It has three continuous parts, the manubrium, the body, and the xiphoid process. The superior border of the manubrium has two clavicular notches for articulation with the clavicles. Seven facets along each side of the sternum articulate with the first seven costal cartilages. (Figure 1-9)