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paranasal sinus

(PAYR-uh-NAY-zul SY-nus)
One of many small hollow spaces in the bones around the nose. Paranasal sinuses are named after the bones that contain them: frontal (the lower forehead), maxillary (cheekbones), ethmoid (beside the upper nose), and sphenoid (behind the nose). The paranasal sinuses open into the nasal cavity (space inside the nose) and are lined with cells that make mucus to keep the nose from drying out during breathing.
More Information
Anatomy of the paranasal sinuses; drawing shows front and side views of the frontal sinus, ethmoid sinus, maxillary sinus, and sphenoid sinus. The nasal cavity and pharynx (throat) are also shown.Enlarge this image in new window
Anatomy of the paranasal sinuses (spaces between the bones around the nose).
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