Anatomic and physiologic considerations in sinusitis.

The anatomy and physiology of the nose, the paranasal sinuses, and related structures are of major importance in understanding sinusitis. A brief description of the airflow, blood flow, nasal cycle, histology and the developmental anatomy are given. These elements combine to condition inhaled air by warming, humidifying, and filtering it. An important mechanism for understanding sinusitis is mucociliary clearance. The nasal cavity and the paranasal sinuses are covered by a pseudostratified, columnar, ciliated epithelium with a thin mucous layer on top of it. In the sinuses the beat of the cilia is directed toward their natural ostia. The ostia of most of the paranasal sinuses lead into the region of the middle meatus and the anterior ethmoid, the osteomeatal complex. Obstruction in this area reduces clearance and plays a major role in the pathophysiology of sinusitis.