Maxillary sinuses

The maxillary sinuses are a pair of air-filled cavities located within the maxillary bones, which are the bones that form the upper jaw and the lower part of the eye sockets. They are situated below the eyes and on either side of the nose, within the cheekbones. The maxillary sinuses are the largest of the four pairs of paranasal sinuses.

Like other paranasal sinuses, the maxillary 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.