Why tears come in eyes when crying or after much laughter? And why they taste salty?

The second question is more interesting but let’s answer the first question first. There are tear glands beneath the eyelids of both the eyes. Eyelids take some liquid from these glands and give a ‘wet wipe’ to the cornea with each blink of the eyes. If this phenomenon did not take place then cornea would become dehydrated – ultimately resulting in blindness. Further, tears are necessary for removal of dust particles settling on the cornea. But more important is the protection against bacterial infection given by anti bacterial constituents in the tears. After cleaning the eyes with each blink, the tear drops drain into the nose through an internal tube where they are quickly evaporated by breathing. Crying or much leaguing brings pressure on the muscles above tear glands. These muscles in turn ‘squeeze’ tear glands which result in flow of tears, some of which also come out of nose. A flow of cold air on the eyes during winter also causes constriction of the muscles above tear glands bringing tears in the eyes.

The mystery of salty taste of tears lies in the evolution of human beings. Millions of years ago living organisms came into existence in the seas first and after subsequent millions of years their descendants appeared on the land. In order to enable prehistoric marine creatures to live in salty water Nature made all body fluids including blood somewhat saline. That is the reason why any body fluid of human beings has somewhat salty taste. Just as blood is salty the tears are also salty.

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