Ethmoid sinuses

The ethmoid sinuses are a group of air-filled cavities located within the ethmoid bone, which is a thin, delicate bone separating the nasal cavity from the brain. Situated between the eyes and the bridge of the nose, the ethmoid sinuses are part of the paranasal sinus system.

Unlike the other paranasal sinuses, the ethmoid sinuses consist of a complex of multiple small air cells, which are divided into anterior, middle, and posterior groups. The number of ethmoid air cells can vary among individuals, usually ranging from 3 to 18 on each side.

Similar to the other paranasal sinuses, the ethmoid 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.