The tear drainage channel is called the lacrimal duct, which includes the superior lacrimal dots, inferior lacrimal dots, superior lacrimal ducts, inferior lacrimal ducts, lacrimal sac, and nasolacrimal duct. The lacrimal glands secrete tears, which are discharged into the conjunctival sac and then distributed on the surface of the eye through the transient movements of the eyelids, and enter the lacrimal sac through the lacrimal dots and ducts by siphoning, and reach the nasal cavity through the nasolacrimal duct. When you cry, there are not only tears but also nasal snot; when you feel a bitter taste when you order eye drops, etc., it means that the tear duct is open. A common clinical symptom of lacrimal tract pathology is tearing. Nasolacrimal duct obstruction, chronic dacryocystitis, lacrimal duct obstruction, tear duct ectasia, etc. can all cause tearing.