The paranasal sinuses are air-filled spaces located within the bones of the skull, surrounding the nasal cavity. They are named for the bones in which they are found, including the frontal, maxillary, ethmoid, and sphenoid sinuses. These sinuses help to lighten the weight of the skull, produce mucus, and contribute to voice resonance. These sinuses are lined with a mucous membrane that helps trap dust and pathogens, aiding in respiratory health. When they become inflamed or infected, a condition known as sinusitis can occur, leading to symptoms like facial pain, congestion, and headaches.