Eyelashes: Protector of Eyes

Every organ or part of our bodies is designed to perform some biological function for the survival and fitness of our bodies. Some of the organs keep working without our ever noticing it until that organ stops working due to some injury or illness. Only then we realize the importance of that organ. One such part of body is eyelashes.

For centuries the eyes have been recognized as an important part of physical beauty, especially for women. Eyes can communicate without the need of words. The human beings have developed great capabilities of eyes. Attractive women’s eyes are often also associated with favorable social status. And in many cultures long full eye lashes are symbols of beauty. On the other hand, loss of eye lashes is seen as a sign of deficiency in women. And so for centuries women have tried a myriad of methods for making their lashes, longer and fuller.

These beauty part aside, from an anatomy and physiology point of view, however, eye lashes serve several functions. They are intended to keep foreign particles or small insects from entering the eyes and causing damage or irritation. Lashes are attached to eyelids in a curved arc designed to channel water away from the eyes, forming another layer of protection from the environment. Lashes are actually sensitive structures, similar to cats’ whiskers. They trigger the blink reflex response when an object comes too close to the eyes

Lashes are simply hairs that grow from the edge of the eyelid. They are arranged in two or three rows. Each eye has between 100 and 150 individual hairs with upper lids having the greater number. Eyelashes are the widest type of human hair and the most richly pigmented. Each hair is, on average, 8-9 mm long, 7 mm of which extend beyond the eyelid. Lashes grow at a rate of about 0.15 mm per day, which means that if lashes are pulled out they take about eight weeks to fully grow back. Like other human hair, eyelashes are produced from follicles under the skin. Follicles have three stages of growth—an actual growing phase, a declination phase and a shedding phase. Each hair is very strong—capable of supporting 100 grams.

Hair growth in humans is different from hair growth in many mammals that shed their hair all at once. Human hair growth is asynchronous—that is, some follicles are experiencing growth while others are in decline or being shed. The eyelash growth cycle is variable, lasting between five and twelve months. The first phase is called anagen. This is the growing phase and lasts about 45 days on average. The normal length of a person’s lashes is determined by this phase. In the second stage of growth, called catagen, follicle cells undergo programmed cell death, a process that takes about fifteen days. About 3% of all lashes are in this phase at any given time. The lashes then enter a period of rest, telogen, which can last as long as nine months. Up to 15% of hair is in this phase. At the end of this phase lashes are shed in a process labeled exogen. As this phase ends, anagen begins again.

Like all human hair, eyelashes are made of 85% proteins, primarily keratin and melanin. Water makes up 7 % of human hair and 3 percent is composed of lipids. The keratin is made up of eighteen amino acids, 7 percent water, and low concentrations of trace minerals (e.g., iron, zinc, copper).

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s