What is the difference between a true rib and a floating rib?

Rib, any of several pairs of narrow, curved strips of bone (sometimes cartilage) attached dorsally to the vertebrae and, in higher vertebrates, to the breastbone ventrally, to form the bony skeleton, or rib cage, of the chest. The ribs help to protect the internal organs that they enclose and lend support to the trunk musculature.

In humans there are normally 12 pairs of ribs.

• The first seven pairs are attached directly to the sternum by costal cartilages and are called true ribs.

• The 8th, 9th, and 10th pairs—false ribs—do not join the sternum directly but are connected to the 7th rib by cartilage.

• The 11th and 12th pairs—floating ribs—are half the size of the others and do not reach to the front of the body. They do not attach to anything.

Each true rib has a small head with two articular surfaces—one that articulates on the body of the vertebra and a more anterior tubercle that articulates with the tip of the transverse process of the vertebra.