Tears - are made of salt water, as you will known if you have ever licked a finger after wiping them away. They happen when the gland which provides moisture to keep the eyeball rotating properly produces more water than usual. The eye cannot drain all this water as it does normally, so a flood occurs. The gland which makes tears is called the lachrymal gland (Lacryma is the Latin word for tear). It is about the size of an almond nut and is situated above the eye. It opens on to the surface of the eyeball by six or more little ducts. Every time we blink the water is spread over the eye. Any extra water is collected in two little canals at the inner corner of the eye where the upper and lower eyelids join, and carried away to the lachrymal sac near the nose. The tear gland makes more water than usual when stimulated by really pungent smell, like onions, or household ammonia, or by a situation of great emotional stress, be it happy or sad.
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