This is Science in the News, in VOA Special English. I’m Shirley Griffith.
And I’m June Simms. Today we talk about hair. We will tell what hair is, how it grows, and some of the main reasons people lose it.
Hair has always been an important sign of beauty. This is especially true for women. Next to the face, hair is one of the main qualities people look for when they consider a woman’s beauty. Whether long or short, curly or straight, hair often gets a lot of attention.
Each hair on a person’s head grows from a single tube-like hole in the skin called a follicle. People are born with all of the hair follicles they are ever going to have. The average person has about one hundred thousand hair follicles. They begin to form on a fetus around the third month of pregnancy.
The part of the hair under the skin is known as the hair root. The hair sticking out from the skin is known as the hair shaft. The shaft is made up of dead cells that have been pushed up through the root. At the base of the hair root is a small ball-like formation called a bulb. This is where new cells are formed. These cells receive nutrition from the blood supply under the skin.
As new cells form, the older cells are pushed up through the root. In time, the old cells are cut off from the blood supply and begin to form a hard protein called keratin. Keratin is the same protein found in our skin and nails. These dead cells and keratin are what make up the hair shaft. This whole process is what causes hair to grow.
Each hair grows independently of other hairs. There are three periods of hair growth. Not all hairs experience the same period of growth at the same time. The period of active growth is called Anagen. During this period, hair grows at a rate of about three tenths millimeters a day, or one centimeter a month. About 85 percent of hair follicles are going through this process at any given time. This period can last from two to six years.
The Catagen period of hair growth comes next. It is then that hair growth begins to slow down. This period usually lasts two or three weeks. Finally, hair growth comes to a complete stop and the hairs begin to fall out. This period is known as Telogen. It affects about 15 percent of all hairs at a time.
Some hair loss can result from a combination of genetics, aging and hormones. When this happens, the hair growth cycle changes and the hair follicles get smaller. In addition, the hairs may get thinner and shorter. Soon the hairs stop growing completely on some parts of the head. People with this condition usually have family members who have experienced similar hair losses. This kind of hair loss is known as pattern baldness. It is the most common kind of hair loss. The official medical term for the condition is androgenetic alopecia.
It is the most common form of autoimmune disease. In alopecia areata, the body’s defenses against disease attack the hair follicles, resulting in a loss of hair on the scalp and other parts of the body.
Sometimes a person may lose their eyebrows, eyelashes or hair on other parts of the body. This condition is called alopecia areata universalis. It is the rarest form of alopecia.
The National Alopecia Areata Foundation says alopecia areata affects about two percent of the population. About five million people in the United States have the condition. It affects people of all ages and races, and often begins in childhood.
That was true of Kayla Martell, the winner of the Miss Delaware Pageant in 2010. Ms. Martell began losing her hair when she was about 10 years old. By the time she was 13, all of her hair had come out.
Kayla Martell did not win the 2011 Miss America Pageant. But she was one of the top 10 finalists. And her public comments have helped raised public understanding of alopecia.
Scientists are not exactly sure what causes alopecia areata. It is not clear why the body’s white blood cells begin to attack the cells in the hair follicles. There is no cure for the disease and no effective treatment that works for everyone.
Angela Christiano is a professor at Columbia University Medical Center. She also suffers from alopecia areata. She says the study gives hope that there may someday be a cure for the condition.
The researchers studied 1,054 cases from the The National Alopecia Areata Registry. They looked for similarities in the genes that people with different levels of alopecia carry. They found that those with 13 to 14 similar genes had diseases that did not progress. Those with 16 or more similar genes usually progressed to alopecia universalis, or total baldness.
The researchers hope to develop a genetic test to predict the severity of the disease. Professor Christiano says the next step is to repeat the study in future research, with a larger number of patients.
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