Humans have 24 ribs (12 pairs). The first seven sets of ribs, known as "true ribs '' (costae verae) also known as vertebrosternal ribs, are directly attached to the sternum through the costal cartilage. Rib 1 is unique and harder to distinguish than other ribs. It is a short, flat, C - shaped bone. The vertebral attachment can be found just below the neck and the majority of this bone can be found above the level of the clavicle. Ribs 2 through 7 have a more traditional appearance and become longer and less curved as they progress downwards. The following five sets are known as "false ribs '' (costae spuriae), three of these sharing a common cartilaginous connection to the sternum, while the last two (eleventh and twelfth ribs) are termed floating ribs (costae fluctuantes) or vertebral ribs. They are attached to the vertebrae only, and not to the sternum or cartilage coming off of the sternum. Some people lack one of the two pairs of floating ribs, while others have a third pair.
a rib that attaches to the sternum by the cartilage of rib 7
true ribs