Final answer:
The six-letter name for the bony structure separating the oral and nasal passages is the nasal septum, which is made of bone and cartilage.
Step-by-step explanation:
The six-letter name for the bony structure that separates humans' oral and nasal passages is the nasal septum. The nasal septum is a wall composed of bone and cartilage that separates the left and right nasal cavities. Anteriorly, it is formed by a portion of the septal cartilage, which you can feel with your fingers. Posteriorly, it includes the perpendicular plate of the ethmoid bone and the vomer bone. The nasal cavity itself features three bony projections on each lateral wall known as nasal conchae—superior, middle, and inferior—with the purpose of increasing the surface area of the nasal cavity and warming incoming air.