Tears are secreted by the main lacrimal gland, the paracrine gland, the lid gland and the conjunctival cupped cells, of which more than 95% are secreted by the main lacrimal gland. The secretion of tears includes basal secretion and reflex secretion, as follows: 1. Basal secretion: no innervation, day and night, but the amount is relatively small, less than 1 μL per minute on average. 2. Reflex secretion: mainly innervated by the sympathetic and parasympathetic nerves. When the body is locally or systemically stimulated by the mind, it will produce a large amount of tear secretion and form a tearing situation. Under daily circumstances, tear secretion mainly flows through the tear dots, tear ducts, tear sacs and nasolacrimal ducts, and is finally discharged through the lower nasal passage. Because tears are constantly secreted and flowing, and the amount of secretion is relatively small, there is also evaporation from the eye surface, so under normal circumstances you will not see a large amount of tears present, and only when a large amount of tears are produced or the tear duct is obstructed will there be a tearing situation.