What Are Sinuses?
Your sinuses (also called paranasal sinuses) are hollow spaces or air-filled cavities in the skull and the bones around your nose. They are part of your nose and respiratory system, and they connect to your nasal passages. The air you breathe in moves through these passages, sometimes accompanied by unwanted invaders. The sinuses produce the helpful mucus that lubricates your nasal passages and the sinuses themselves.1,3