Fill in the Blanks 1a Thoracic CageOnline version Identify the bones that form the thoracic cage. by Erica Moore 1 thoracic cag xiphoid body 12th true floating manubrium false 6th 1st process The is the superior sternal bone that is triangular in shape . The is the middle sternal bone that extends from T5 - T9 . The is the inferior sternal bone that is thin and pointed . Ribs 1 - 7 attach anteriorly to the sternum via costal cartilage are known as ribs . Ribs 8 - 10 attach by cartilage to the 7th costal cartilage are known as ribs . Ribs 11 - 12 do not attache to the sternum and are known as ribs . The rib is short , broad , flattened , and markedly curved . The rib is a typical rib , it has a head , neck , and shaft . The rib is a short slender bone . Twelve thoracic vertebrae , twelve ribs , and three bones that constitute the sternum , form the