The principle maxillary sinus ostium (PMO) and accessory sinus ostium (i.e., accessory ostium) are the anatomical structures of the middle meatus that are referred to as the osteomeatal complex. This complex contributes to the final drainage pathway of the anterior ethmoidal, maxillary and the frontal sinuses. The principle maxillary sinus ostium is present throughout the … Continue reading Accessory ostium