英语听力文摘 English Digest 314、手茧如何形成？

　　What Are Calluses And How Are They Formed?
皮肤上的茧是如何形成的？
人体皮肤由于劳动过程长期摩擦造成皮肤表皮细胞坏死而形成的，主要出现于手掌、足掌等部位。长时间的受到磨檫,组织细胞的老死,角质层的严重受损形成手茧．
Most of us are familiar with calluses.
These extra-tough patches of skin are generally quite useful–we might even say handy–because they act like a kind of natural armor, protecting areas of skin that get an unusual amount of wear and tear. Have you ever wondered exactly what a callus is, or how it forms on your skin?
Callus formation is triggered by pressure or abrasion¹. The heel of your foot as it rubs inside your shoe, or the palm of your hand if you’re doing a lot of manual labor² are good examples of this.
While it might feel like a callus is something extra, added to your skin, it’s actually just a build-up of what’s already there.
Here’s How It Works
Your skin has a number of layers of different types of cells.
The outermost³ is a layer of hardened, dead cells. This top layer is usually about twenty-five cells thick, and it constantly replaces itself as the outermost cells flake⁴ off to be replaced by new hardened, dead cells underneath⁵.

　　All About Friction⁶
If your skin is subject to an unusual amount of friction, this layer of dead cells increases. New dead cells are added faster than the old ones slough⁷ away. This can build up the outer layer from twenty-five cells thick to over a hundred cells thick. You’ve grown a callus.
While calluses are generally useful, if the process continues unchecked a callus can thicken into a cone-shaped structure called a corn. These super calluses can be quite painful, and may require the attention of a doctor.
译文
对于“老茧”，我们都很熟悉。
这些皮肤上突出的硬皮是很有用的，也可以说是方便，因为他们扮演着保护常磨损皮肤的天然盔甲的角色。你是否思考过什么是老茧？他又是怎样形成的？
老茧是由压力和摩擦而形成。脚后跟的茧是由其在鞋里摩擦而形成，正如手茧是在大量的劳动过程中形成。
尽管看起来似乎是皮肤上多出的部分，然而事实是已经存在的皮肤角质的累积。
形成过程
皮肤是由若干层不同类型的皮肤构成。
表层是一些坏死的硬细胞，通常有25个细胞那么厚，表层细胞不断的脱落，取而代之的是下层硬的坏死细胞，由此而完成自我更替过程。
一切皆由摩擦引起
假如皮肤受到不寻常量的摩擦，这层坏死细胞将会增加，新的坏死细胞增长速度比旧细胞脱落的速度快，这就致使皮肤表层的厚度增加到100个细胞那么厚，由此，老茧便形成。
虽然一般来讲，茧是有益的，但如不控制其过程，老茧厚度就会增加到被称作鸡眼的锥形结构，那样就会很疼，甚至需要去看医生。

1 abrasion   

n.磨（擦）破，表面磨损

参考例句：

• Diamonds have extreme resistance to abrasion.钻石极抗磨损。
• This analysis is helpful to the research of derailment and abrasion machenism.该分析有助于脱轨和磨耗机理的探讨。

2 labor   

n.劳动，努力，工作，劳工；分娩；vi.劳动，努力，苦干；vt.详细分析；麻烦

参考例句：

• We are never late in satisfying him for his labor.我们从不延误付给他劳动报酬。
• He was completely spent after two weeks of hard labor.艰苦劳动两周后，他已经疲惫不堪了。

3 outermost   

adj.最外面的，远离中心的

参考例句：

• He fired and hit the outermost ring of the target.他开枪射中了靶子的最外一环。
• The outermost electron is shielded from the nucleus.原子核对最外层电子的作用受到屏蔽。

4 flake   

v.使成薄片；雪片般落下；n.薄片

参考例句：

• Drain the salmon,discard the skin,crush the bones and flake the salmon with a fork.将鲑鱼沥干，去表皮，粉碎鱼骨并用餐叉子将鱼肉切成小薄片状。
• The paint's beginning to flake.油漆开始剥落了。

5 underneath   

adj.在...下面，在...底下；adv.在下面

参考例句：

• Working underneath the car is always a messy job.在汽车底下工作是件脏活。
• She wore a coat with a dress underneath.她穿着一件大衣，里面套着一条连衣裙。

6 friction   

n.摩擦，摩擦力

参考例句：

• When Joan returned to work,the friction between them increased.琼回来工作后，他们之间的摩擦加剧了。
• Friction acts on moving bodies and brings them to a stop.摩擦力作用于运动着的物体，并使其停止。

7 slough   

v.蜕皮，脱落，抛弃

参考例句：

• He was not able to slough off the memories of the past.他无法忘记过去。
• A cicada throws its slough.蝉是要蜕皮的。