The inspired air flowing through the superior nasal meatus results in a negative pressure.This force drags in tear flow which is facilitated by mucociliary apparatus.

• 吸气时，经由上鼻道之气流，于瘘管开口形成负压，此力量将泪液曳引流入上鼻道，同时由黏膜纤毛之组识结构助畅其流。