Sabtu, 30 Januari 2010

TEARS



Tears are the liquid product of a process of crying to clean and lubricate the eyes. The word lacrimation (from L. Lacrima meaning Tear) (also spelled lachrymation) may also be used in a medical or literary sense to refer to crying. Strong emotions, such as sorrow or elation, may lead to crying. The process of yawning may also result in lacrimation. Although most land mammals have a lacrimation system to keep their eyes moist and in response to other stimuli, humans are the only mammal generally accepted to cry emotional tears



DISCUSSION

Tears flow from tear glands into your eyes through tiny tear ducts. The tear glands are located under your upper lids, and when stimulated, produce tears to form a thin film over your eyeballs. Every time you blink the film spreads over your eyes to keep them moist and free of dust and other irritants. Whether you are awake or asleep, happy or sad, this salty fluid is always flowing from the tear glands.

Besides protecting your eyes, the tear glands produce more fluid when your eyes are irritated. These extra tears are called reflex or irritant tears. And, when something makes you happy or sad, your tear glands will produce emotional tears. Used tears then drain down into two tiny openings on the brim of your upper and lower eyelids at the inner edge of your eyes, which lead to the nasolacrimal tear ducts next to the bridge of your nose. From there, they are channeled into your nasal cavity where they are swallowed or blown out with other nasal fluids. If there are too many tears, they will overflow your lower lid and run down your cheeks.

Some people have to help stimulate the production of natural tears. This disease is called Dry Eye Syndrome or Sjogren's Syndrome. People who have diseases like rheumatoid arthritis or lupus often have this condition. They must use artificial tears up to every 10 to 15 minutes, and apply other medications to their eyes before going to bed as part of the treatment to improve the condition of their eyes.

Things to Talk About

1. In the "Newton's Apple" segment on tears, a woman talked about having Dry Eye Syndrome. During the daytime, she must put special eye drops (artificial tears) in her eyes about every hour. Think about the things you do and the places you go where your eyes need protection. How would they change if you had Dry Eye Syndrome and had to use eye drops that often? What would it feel like to do something very often that other people don't even have to think about?
2. If Dry Eye Syndrome goes untreated it can cause blindness. What other seemingly insignificant things, such as not being able to cry, could result in such dramatic results?
3. Humans are the only animals that cry emotional tears. Do you think these tears have any other biological purpose? What might this purpose be?
4. What does someone who's been crying look like?

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