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一般说来,年轻人的头发乌黑油亮,而老年人往往白发苍苍。头发乌黑是因为头发里含有一种黑色素,黑色素含量越多,头发的颜色就越黑;反之,黑色素含量越少,头发的颜色就越淡。随着人体的衰老,毛囊中的色素细胞将停止产生黑色素,头发也就开始变白。人体没有统一分泌黑色素的腺体,黑色素在每根头发中分别产生,所以头发总是一根一根地变白。一般头发
In general, young people have shiny black hair, while older people tend to be gray-haired. Black hair is because the hair contains a melanin, the more the content of melanin, the hair color is more black; the other hand, the less the content of melanin, the lighter the hair color. As the human body ages, the pigment cells in the hair follicle stop producing melanin, and the hair begins to whiten. The human body does not have a uniform secretion of melanin glands, melanin produced in each hair, so the hair is always white one by one. Normal hair