What is the purpose of tears and crying?

Tears flow from glands (the lacrimal glands) arranged around the eyes, and these glands are constantly releasing a small amount of liquid to wash away things like dirt or dust that settle on the front of the eyes. This constant flow of liquid moisturizes the eyes and helps keep vision clear. We produce tears whether we are awake, asleep, happy, or sad. Tears that are produced when our eyes are irritated, for example by onions, are called reflex tears; emotional tears occur when we have strong feelings.

The main lacrimal glands are located underneath the bony areas of the skull beneath the outer edges of the eyebrows. Tiny ducts, which line the upper and lower eyelids and the inner edges of the eyelids next to the nose, carry tear fluid from the tear glands to the surface of the eyes and then drain into the nasal cavity and then into the throat. The amount of fluid in these tubes is normally small, and we rarely notice the extra fluid in the nose. However, when we cry, excess tears flow through the system, which explains runny noses and voice changes that are usually associated with crying.

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