What bone forms the posterior/inferior part of the nasal septal wall between the nostrils?

The vomer is the bone that forms the posterior and inferior part of the nasal septum, which separates the two nasal cavities. It is a thin, plow-shaped bone that is located in the midline of the nasal cavity and articulates with other structures, including the sphenoid and the maxilla. The vomer plays a crucial role in the anatomy of the nasal cavity by providing structure and support to the septum.

In contrast, the palatine bones are primarily involved in forming the hard palate and do not contribute significantly to the nasal septum. The maxilla, while also contributing to the structure of the nasal cavity, forms the upper jaw and does not provide the posterior-inferior support that the vomer does. The sphenoid bone has a more complex relationship with the skull and houses important structures such as the pituitary gland, but it does not form part of the nasal septum. Therefore, the vomer's specific location and function make it the correct answer.