Most tears are produced by the lacrimal glands in the eye. A lacrimal gland lies at the upper, outer corner of each orbit. Every time a person blinks, the eyelids spread a smooth layer of mucus and tears over the eye. These fluids then flow into tiny canals in the lids. The canals lead to the lacrimal sac, a pouch at the lower, inner corner of each orbit.

From the lacrimal sac, the mucus and tears drain through a passage into the nose. After crying, a person may have to blow the nose to clear this drainage system of the excess amount of tears. The conjunctiva is a membrane that lines the inside of the eyelids and extends over the front of the white part of the eye. It produces mucus, a clear, slimy fluid that lubricates the eyeball. The conjunctiva also produces some tears, which help keep the eyes clean.

So how often should we shed tears to keep the eyes clean?