Tears are produced by the tear glands in the upper eyelids at a regular rate. Tear glands are also known as lacrimal glands. Each gland is about the size of shelled-almond and is divided into upper and lower portion.
Tears are actually salty fluid full of protein, mucus, water and oil. There are different kinds of tears – basal tears, reflex tears and emotional tears.
There are two ducts upper and lower at the end of upper and lower lid margins. Tears come out of the ducts through the openings into the surface of eye. Any decrease in the tear secretion leads to dry eyes. Tears are anti-bacterial that keeps the surface of eye moisturized. They provide some oxygen to surface structures and possess anti-bacterial properties.
We think tears come out when we feel stressed out. But there are other times too when tears are produced. Basal tears are those that keep our eyes from drying out. Reflex tears help protect human eye from certain irritants. Last type is the emotional tears that come out due to stress or sadness.
Crocodiles have a strange behavior of shedding tears while eating food. It is found that while they eat either the result of actions caused by their mouth results in a flow of air that stimulates the glands to over produce tears or that the movement of their head while munching may result in production of tears.