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science divides tears in three types; Basel tears, reflex tears and emotional tears. And that the tear fluid of all tear types consists of: water, lipids, glucose, mucin, lactoferrin, lipocalin, lacritin, immunoglobulins, urea, sodium, potassium, chloride, manganese and lysozyme.
But that there was one exception, the emotional tear, it contains more then the contents above, it also contains: Prolactin, adrenocorticotropic and leucine enkephalin (a natural painkiller)

So 1 part is that different kinds of tears contain different kinds of things + temperature + humidity together with the unique physiology of the body make up for different tear shapes.