Purpose of Eyelashes
Not many people know the reason for the existence of eyelashes. It is easy to think that they are a practically useless appendage that happens to be quite a lovely adornment. Those who lack eyelashes, however can suffer from a great many eye conditions. Contrary to what some may think, eyelashes do have an important function and are a vital part of the human anatomy.
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Definition
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Eyelashes are a row of tiny hairs that line the ridge of the upper and lower eyelids. Each eyelid contains 70 to 150 eyelashes and are constantly going through cycles of loss and growth--from the Anagen phase, which is the growth period, to the Catagen phase, in which the follicle shrinks, to the Telogen phase, the rest cycle. The eyelashes then fall out and are replaced within a few months. The eyelashes are not coordinated in this cycle, and each one can be at any phase at any given time.
Occurence
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Eyelashes are typically found in most mammals, including giraffes and camels, whose eyelashes are particularly long and thick. Some birds and reptiles also have been found to have "eyelashes" of a sort. In birds, such as the hornbill, this is usually a type of feather. In reptiles, most notably the eyelash viper, these are a few elongated scales over the eyes.
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Function
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Eyelashes help to serve a number of practical purposes. One is that they block any debris and sweat from entering the eye, thus preventing the scratching of the cornea and other irritation. Another is that they assist in detecting any foreign objects approaching the eye itself, prompting the reflex of the eyelid to shut.
Cosmetic
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In many cultures, long eyelashes are considered a symbol of femininity, innocence and glamour and are particularly coveted among women. There are many products available on the market, from mascara to eyelash curlers to false eyelashes for the purposes of enhancing one's own eyelashes. There is also a procedure to temporarily extend the eyelashes.
Conditions
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There are many medical conditions associated with the eyelashes. Madarosis, for example, is a chronic condition in which eyelashes are constantly lost in large quantities. This occurs often in people who suffer from Hyperthyroidism. Another medical condition is Distichiasis, in which the eyelashes grow in places other than the eyelid ridge.
Eyelashes also can become ingrown, which leads to pain, irritation and infections of the hair follicles.
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Resources
- Photo Credit DeGeorge Photography
