The sinuses are air filled spaces in the skull. Most people do not realize these spaces exist in the skull until a problem develops, and they begin to experience the symptoms of sinusitis.
There are 4 pairs of sinuses,
- Maxillary sinus – behind the cheeks
- Ethmoid sinus – between the eyes behind the bridge of the nose
The other two develop later:
- Frontal sinus – Developed around the age of seven, these are located in the area of the forehead, over the brow.
- Sphenoid sinus – Developed during adolescence, a last pair deep in the centre of the head (sphenoid).
The sinuses are connected to the nose and nasal cavity by way of small openings called ostia. Except for the ethmoid sinuses between the eyes, the other sinuses are poorly developed at birth. They normally commence development in later childhood to attain their adult size at the onset of puberty.