你也开始脱发了吗？科学家说了，我们还有救的！ | 周末涨知识
你今天脱发了吗？
90后的年轻一代已然成为脱发大军的主力，那么究竟是什么叫人头秃，让秀发离你而去呢？
你知不知道头发居然也有自己的生长期！日渐发亮的头顶还有没有希望恢复往日生机？这则TED科普给你答案。
认识头发
人的头上一般有多少根头发？它们是由什么组成的呢？
The full-headed among us have about 100,000 to 150,000 strands of hair on our scalps.
长满头发的人的头皮上大概有10万到15万根头发。
对于这片厚厚的灌木丛，科学家有两个新发现。
First, the sprouting hair we see is mostly made up of keratin, the protein left over from dead cells forced upward as new cells grow beneath them.
首先，我们看到的长出的头发，主要由角质组成的。角质就是因为新细胞在它们之下生长而被向上推的死细胞中剩余的蛋白质。
Second, the structures that drive hair growth are called hair follicles, a network of complex organs that form before our birth and promote the everlasting growth cycle of hair.
其次，使头发生长的结构叫发囊。发囊是复杂器官组成的一个网络，它在我们出生之前就形成了，它能使头发循环往复不断生长。
头发的生长周期
头发有自己的生长周期，分为三个阶段，即生长期、倒退期和终止期。
生长期
The first is anagen, the growth phase, which up to 90% of your hair follicles are experiencing right now, causing them to push up hair at a rate of one centimeter per month.
第一阶段是毛发生长初期，即生长期。多达90%的发囊正处于毛发生长初期，它们以每月一厘米的速度把头发向上推。
Anagen can last for two to seven years depending on your genes.
根据每个人基因的不同，毛发生长初期可以持续2到7年。
倒退期
After this productive period, signals within the skin instruct some follicles to enter a new phase known as catagen, or the regressing stage, causing hair follicles to shrink to a fraction of their original length.
经历过这个高产阶段之后，皮肤会发出信号，命令一些发囊进入一个新的阶段。这个阶段叫做毛发生长中期，或者倒退期。倒退期使发囊缩小至它们原来长度的一小段。
Catagen lasts for about two to three weeks and cuts blood supply to the follicle, creating a club hair that’s ready to be shed.
这个阶段持续2到3周，并切断毛囊的供血，使其形成一个杵状毛，这意味着头发已经准备好要脱落了。
休止期
Finally, hairs enter telogen, the resting phase, which lasts for ten to twelve weeks, and affects about 5-15% of your scalp follicles. During telogen, up to 200 club hairs can be shed in a day, which is quite normal. Then, the growth cycle begins anew.
最后，头发进入毛发生长终期，即休止期，持续10至12周，并影响到你5%到15%的头皮毛囊。在毛发生长终期，多达200跟杵状毛会在一天之内脱落，这是十分正常的。然后，生长周期又重新开始。
秃顶与DHT
秃顶和脱发的罪魁祸首究竟是谁？DHT你需要了解一下：
Not all heads are hairy, and in fact, some of them grow increasingly patchy over time in response to bodily changes.
不是所有人的脑袋都是毛发旺盛的，实际上，随着时间的推移，有些人的头逐渐一块一块地变秃了。这是对身体变化做出的反应。
Some 95% of baldness in men can be attributed to male pattern baldness. Baldness is inherited, and in people with this condition, follicles become incredibly sensitive to the effects of dihydrotestosterone（DHT）, a hormonal product made from testosterone.
男性中95%的脱发是由于男性型秃。秃顶是遗传的，有男性型秃的人，他们的发囊会变得对二氢睾酮（DHT）异常敏感。二氢睾酮是从睾酮中产生的激素。
DHT causes shrinkage in these overly sensitive follicles, making hair shorter and wispier. But loss isn’t sudden. It happens gradually, along a metric known as theNorwood Scale, which describes the severity of hair loss.
二氢睾酮导致这些过于敏感的毛囊缩小，使头发变得又短又细。但脱发不是一夜之间就脱掉的，它根据一个度量标准逐渐发生，这个度量叫诺伍德量表，用来衡量脱发的严重程度。
脱发的历程
所以，脱发也有其规律，按照诺伍德量表的度量标准逐渐发生，沿着太阳穴脱落，从头顶开始变稀疏。
First, hair recedes along the temple. Then hair on the crown begins to thin in a circular pattern.
首先，头发沿着太阳穴脱落，然后，头顶的头发一圈一圈地变稀疏。
At the highest rating on the scale, these balding areas meet and expand dramatically, eventually leaving only a ring of sparse hair around the temples and the back of the head.
达到这个量表的最高级时，秃了的部分相互连接然后大幅扩张，最后只剩下太阳穴周边一圈稀少的头发和后脑勺的头发。
脱发原因
除了遗传基因导致脱发，长期处于高压状态下也会使头发提前进入休止期哦！所以保持乐观心态对于保护头发也是十分重要的！
Genetics isn’t all that drives hair loss.
基因不是导致脱发的唯一原因。
Long periods of stress can release signals that shock follicles and force them into a resting phase prematurely.
长期的压力会释放刺激毛囊的信号，并且使他们提早进入休止期。
Some women experience this after childbirth. Follicles might also lose the ability to go into anagen, the growth phase.
一些产后妇女会经历这个阶段。发囊也有可能失去能力，无法进入毛发生长初期，即生长期。
People going through chemotherapy treatment temporarily experience this.
接受化疗的人会暂时经历这个阶段。
脱发的治疗
已经在脱发的小伙伴千万不要放弃自己，因为科学家说了，你们还有希望！
But while balding may look permanent, scientific investigation has revealed the opposite.
虽然脱发也许看起来是永久性的，但科学研究却揭示出相反的一面。
脱发的治疗主要使通过缩短头发的休止期，限制睾酮转变成二氢睾酮的方法来实现。
Below the skin’s surface, the roots that give rise to our hair actually remain alive. Using this knowledge, scientists have developed drugs that shorten the resting phase, and force follicles into anagen. Other drugs combat male pattern baldness by blocking the conversion of testosterone to DHT, so that it doesn’t affect those sensitive follicles.
在表皮下，使我们头发生长的发根实际上仍保持着活性。运用这个知识，科学家们发明了可以缩短休止期的药物，迫使发囊进入毛发生长初期。其它治疗男性型秃的药物，通过限制睾酮转变成二氢睾酮的方法来实现，这样敏感的发囊就不会受到影响。
Stem cellsalso play a role in regulating the growth cycle, and so scientists are investigating whether they can manipulate the activity of these cells to encourage follicles to start producing hair again.
干细胞也起到调整生长周期的作用，所以科学家们正在研究他们是否可以控制这些细胞的活动，从而促使这些毛囊重新开始长出头发。
不过，就算秃了，也不要太过焦虑……
And in the meantime, while scientists hone their hair-reviving methods, anyone going bald or considering baldness can remember that they’re in great company.
同时，当科学家在研究头发再生的方法时，秃顶者或为秃顶焦虑的人，请记住，你们还有一群伟大的人物相伴。
脱发不可怕，因为还有一群智商超群的伟大人物与你相伴！
编辑：左卓
实习生：郭镇
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