Sinus Anatomy & Function

The sinuses are air filled cavities located in the face and around the nose. The sinuses are named according to the bone in which they are located.

grosssinus

There are four paired sinus cavities. The maxillary sinuses are located in each cheek bone. The ethmoid sinuses are located between the eyes. The frontal sinuses are in the forehead above the eyes. The sphenoid sinuses are in the back of the head, located behind the ethmoid. They drain into the nose via specific openings called ostia. The goal of Functional Endoscopic Sinus Surgery is to maximize the size of these ostia.

Children have maxillary and ethmoid sinuses, however, the sphenoid and frontal sinuses develop during the teenage years.

Sinuses serve many functions. They first filter and humidify the air we breath. In evolutionary terms, they lighten the weight of the head. They also protect our vitals structures in trauma situations functioning as crumple zones.

The nasal septum divides the nose into two separate nasal cavities. The side of the nose contains three structures called turbinates. The turbinates are named for their location in the nose, inferior (lower), middle and superior (upper). Inferior turbinate enlargement will result in patients complaining of nasal obstruction. The main function of turbinates is to provide humidification and provide mucus production for the nose.

The nose and sinuses are covered with a complex lining that is lined with millions of cilia. The lining secretes mucus which functions to keep the nose moist and has properties to capture and eliminate allergens and certain viruses/bacteria. The cilia sweep mucus in a choreographed fashion to eliminate irritants in the nose and sinuses. When the cilia are damaged, patients develop chronic sinusitis. Cilia are damaged by viruses, tobacco, genetic illnesses (cystic fibrosis), allergens, bacteria and certain chemicals. Ciliary damage is a difficult and complicated problem to manage.

cilia 3500X

Electron micrograph of sinus mucosa demonstrating hair-like cilia projections