Final answer:
The bony structures that help filter and warm incoming air in the respiratory tract are the turbinates, specifically the inferior nasal conchae, which are part of the cranial bones.
Step-by-step explanation:
The structures formed by the cranial bones that prevent contaminants from entering the respiratory tract are called turbinates, specifically the inferior nasal conchae. The turbinates, with the help of the paranasal sinuses, ensure that the air we breathe is filtered and conditioned before it reaches the lungs. Each paranasal sinus is named for its associated bone: frontal sinus, maxillary sinus, sphenoidal sinus, and ethmoidal sinus.
These bony projections, which also include the superior and middle nasal conchae, increase the surface area of the nasal cavity and help to clean, warm, and moisten the incoming air. The inferior conchae are independent bones, while the superior and middle conchae are part of the ethmoid bone. These sinuses have a lining of mucosa, which helps prevent contaminants from entering the respiratory tract.