Sinuses are hollow spaces within the facial bones. They are lined with a ciliated mucosa which has mucus glands. The sinuses are interconnected via a series of openings, allowing mucus to drain into the nose and pharynx.
The sinuses help to warm inhaled air before it enters the lungs.
Sinuses are prone to infection or reaction to allergens and react by mucosal swelling and overproduction of mucus. Chronic inflammation or infection can result in permanent thickening of the mucosa and reactive bone changes. Surgery is designed to facilitate drainage and relieve pressure; in some patients it must be repeated a large number of times.