All of us cry when we fell sad or are hurt. but have you ever thought of how the tears actually come? The fact is, our tear glands are constantly producing tears, but they do not overflow. Tears have a very important function- they protect our eyes from infections as they are mildly antiseptic. They do this by constantly bathing our eyes gently, and then draining away through the tear dusts to the tear sacs and the cavity of the nose.
When we are upset or pain, our tear dusts produce tears faster than they can drain away. So, they flow down our checks instead, and when this happens, we cry.