Rib
Ribs are classed as flat bones which usually have a protective role in the body. Humans have 24 ribs, in 12 pairs. All are attached at the back to the thoracic vertebrae, and are numbered from 1–12 according to the vertebrae they attach to. The first rib is attached to thoracic vertebra 1 (T1). At the front of the body most of the ribs are joined by costal cartilages to the sternum. The ribs connect to the vertebrae with two joints, the costovertebral joints.
Cephalopod limb
In the scientific literature, a cephalopod "arm" is often treated as distinct from a "tentacle", though the terms are sometimes used interchangeably. Generally, arms have suckers along most of their length, as opposed to tentacles, which have suckers only near their ends. Barring a few exceptions, octopuses have eight arms and no tentacles, while squid and cuttlefish have eight arms (or two "legs" and six "arms") and two tentacles. The limbs of nautiluses, which number around 90 and lack suckers altogether, are called tentacles.