The paranasal sinuses are eight (four pairs) air-filled spaces, or sinuses, within the bones of the skull and face. These are divided into subgroups that are named according to which bones they lie under;
- the maxilliary sinuses, also called the antra, are under the eyes, in the upper jawbone.
- the frontal sinuses, over the eyes, in the bone of the forehead.
- the ethmoid sinuses, between the nose and the eyes, backwards into the skull.
- the sphenoid sinuses, in the centre of the skull base.
- Decreasing the relative weight of the front of the skull
- Helping to warm and humidify inhaled air before it reaches the lungs
- Increasing resonance of the voice.