Sphenoid sinuses

The sphenoid sinuses are a pair of air-filled cavities located within the sphenoid bone, which is a butterfly-shaped bone at the base of the skull, situated deep behind the eyes and the ethmoid sinuses. They are part of the paranasal sinus system.

The sphenoid sinuses vary in size and shape among individuals, and their development continues through adolescence, reaching full size in adulthood. Like other paranasal sinuses, the sphenoid sinuses are lined with a mucous membrane that produces mucus to help humidify the air we breathe, trap particles like dust or allergens, and provide some immune defence against pathogens. The mucous membrane also contains cilia, tiny hair-like structures that move mucus towards small openings called ostia. Through these ostia, mucus drains into the nasal cavity, and air can circulate between the nasal cavity and the sinuses.