The sinuses are hollow, air-filled cavities located in the bones around the nose and eyes. There are four pairs of paranasal sinuses, each named for the bone in which they are found:

• Frontal sinuses : Located above the eyes, in the frontal bone of the forehead, just above each eye

• Maxillary sinuses : The largest sinuses, located under the eyes in the cheekbones (maxillary bones), near the upper jaw

• Ethmoid sinuses : A group of small air cells located between the eyes, within the ethmoid bone, near the bridge of the nose

• Sphenoid sinuses : Located deeper in the skull behind the eyes, within the sphenoid bone near the optic nerve and pituitary gland

These sinuses surround the nasal cavity and connect to it, playing roles in mucus production, humidifying air, lightening the skull, and voice resonance