Final answer:
Ribs 1-7 are true ribs attaching directly to the sternum, while ribs 11 and 12 are floating ribs lacking anterior attachments to the sternum or other ribs.
Step-by-step explanation:
The statement about ribs numbered 11 and 12 being true ribs is incorrect. In fact, ribs 1-7 are classified as true ribs or vertebrosternal ribs, meaning they attach directly to the sternum via their costal cartilage. Ribs numbered 11 and 12 are known as floating ribs or vertebral ribs. These ribs do not have anterior attachments to the sternum or to the costal cartilage of another rib. Instead, their costal cartilages terminate within the musculature of the lateral abdominal wall, giving them the 'floating' designation.
Therefore, ribs 11 and 12 cannot be categorized as true ribs because they lack the direct sternum connection characteristic of ribs 1 through 7. These floating ribs provide protection for the kidneys and assist with the breathing process, despite not being connected to the sternum or the anterior thoracic wall.