Frontal sinuses

The frontal sinuses are a pair of air-filled cavities located within the frontal bone of the skull, above the eyebrows and behind the forehead. They are part of the paranasal sinus system, which also includes the maxillary, ethmoid, and sphenoid sinuses.

The frontal sinuses vary in size and shape among individuals and are typically asymmetrical. They are lined with a mucous membrane, which 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, which are hair-like structures that help 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.