The appendicular skeletal system is the series of bones that form the arms and legs. These appendages are connected to the axial or central skeleton vertebrae and ribs by a series of bones that are collectively called the girdles. There is strong evolutionary evidence that suggests vertebrates are descendants of a group of fish named the Rhipidistians. Both the fossil and living fish have the same kind of bone structure and sequence of bone types in their fin girdles. It is believed that as these bones became increasingly functional in body weight support that they adapted to a variety of vertebrate functions.

The human pectoral girdle supports the arms. The broad and flat scapula attaches to the back of the body in the thoracic or chest region. Large muscles of the neck and back are anchored to it. In the front (anterior) region of the chest...