BARBARA KLEIN: 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 eighty five percent of hair follicles are going through this process at any given time. This period can last from two to six years.
STEVE EMBER: 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 fifteen percent of all hairs at a time.
On average, a person loses between fifty and one hundred hairs every day. Since each hair grows at a different rate, this process is overlooked. Once the telogen period has ended, the hair growth process begins again.
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BARBARA KLEIN: So what happens when a person has trouble growing hair or suffers from hair loss? Your genes control how fast or how long your hair will grow. Some people have a longer than usual anagen growth period. These people may be able to grow more hair than the average person. However, others struggle to grow shoulder length hair. These people have a shorter than normal anagen period.
最新
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25
2013-11-25