Costa

Human ribs are flat bones that form part of the rib cage to help protect internal organs.

Humans usually have 24 ribs, in 12 pairs. 1 in 500 people have an extra rib known as a cervical rib.

All are attached at the back to the thoracic vertebrae and are numbered from 1–12 according to the vertebrae to which they attach.

The first rib is attached to thoracic vertebra 1 (T1).

At the front of the body, most of the ribs are joined by costal cartilage to the sternum.

Ribs connect to vertebrae at the costovertebral joints.

The parts of a rib include the head, neck, body (or shaft), tubercle, and angle.

The head of the rib lies next to a vertebra.

The ribs connect to the vertebrae with two costovertebral joints, one on the head and one on the neck.

The head of the rib has a superior and an inferior articulating region, separated by a crest.

These articulate with the superior and inferior costal facets on the connecting vertebrae.

The crest gives attachment to the intra-articulate ligament that joins the rib to the vertebra of the same number, at the intervertebral disc.

Another ligament, the radiate ligament joins the head of the rib to both the body of the upper vertebra and to the body of the lower vertebra.

The smaller middle part of the ligament connects to the intervertebral disc.

This plane joint is known as the articulation of the head of the rib.

The other costovertebral joint is that between the tubercle on the neck and the transverse process of the joining thoracic vertebra of the same rib number, and this is known as the costotransverse joint.