Final answer:
Ribs 10, 11, and 12 are atypical because they don't articulate with the sternum, they are shorter and more curved, and they lack articulation with the transverse processes of the thoracic vertebrae.
Step-by-step explanation:
Ribs 10, 11, and 12 are considered atypical because:
- They don't articulate with the sternum.
- They are shorter and more curved compared to the other ribs.
- They don't articulate with the transverse processes of the thoracic vertebrae.
These characteristics differentiate them from the typical ribs, which have different articulations and shapes.