Final answer:
The ethmoid and vomer bones make up the back of the nasal septum, with the ethmoid contributing to the upper part and the vomer to the lower part.
Step-by-step explanation:
The two bones that make up the back of the nasal septum are the perpendicular plate of the ethmoid bone and the vomer bone. The ethmoid bone contributes to the upper portion of the nasal septum, while the vomer bone forms the lower and posterior parts of the nasal septum. These bones are complemented by the septal cartilage in a living organism, but in a dry skull, only the bony structures are observable.