a mucus-lined air cavity in a skull bone; communicates with the nasal cavity; the paranasal sinuses are located in the frontal, maxillary, ethmoid, and spenoid bones

any of the paired sinuses in the bones of the face adjacent to the nasal cavity that are lined with mucous membrane that is continuous with lining of the nasal cavities

sinuses surrounding the nose that help to warm and moisten inhaled air.

an air-filled cavity within the skull; there are 4 sets of paranasal sinuses: frontal, maxillary, sphenoidal and ethmoid.

Paranasal sinuses are air-filled spaces, communicating with the nasal cavity, within the bones of the skull and face.