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.
Limb (anatomy)
Human legs and feet are specialized for two-legged locomotion – most other mammals walk and run on all four limbs. Human arms are weaker, but very mobile allowing us to reach at a wide range of distances and angles, and end in specialized hands capable of grasping and fine manipulation of objects.