Rene Meadows, age 11, of Dubuque, Iowa, for her question:

WHAT EXACTLY ARE TEARS?

Tears are the secretion of the lachrymal glands. Tears continually bathe the cornea, the tough outer layer of the eyeball.

Tears help clear the eyeball of foreign particles such as dust and hairs, and they also help to keep it from drying out, which would result in blindness.

One lachrymal gland lies behind each eyelid. The two pour out their fluid through several small ducts in the underside of the lid. Each time the lid blinks, it sucks a little fluid from the glands.

When a person feels some emotion, such as grief or anger, the muscles around the lachrymal glands may tighten up and squeeze out tears. This can happen when a person cries in sadness or with a hearty laugh.