The sphenoidal sinuses are a pair of air-filled spaces located within the sphenoid bone, which is situated behind the nose and between the eyes. These sinuses are part of the paranasal sinus system and help to lighten the weight of the skull, improve voice resonance, and provide insulation for surrounding structures. Each sphenoidal sinus drains into the nasal cavity through small openings. They are lined with mucous membranes that produce mucus, which helps trap dust and pathogens. Inflammation or infection of these sinuses can lead to conditions such as sinusitis, causing symptoms like headache and facial pain.