时差N小时 你的手上有老茧吗?(下)（在线收听）

The outermost is a layer of hardened, dead cells.

表层是一些坏死的硬细胞，

This top layer is usually about twenty-five cells thick, and it constantly replaces itself as the outermost cells flake off to be replaced by new hardened, dead cells underneath.

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。

If your skin is subject to an unusual amount of friction, this layer of dead cells increases.

假如皮肤受到不寻常量的摩擦，这层坏死细胞将会增加，

New dead cells are added faster than the old ones slough away.

新的坏死细胞增长速度比旧细胞脱落的速度快，

This can build up the outer layer from twenty-five cells thick to over a hundred cells thick.

这就致使皮肤表层的厚度增加到100个细胞那么厚，

You've grown a callus.

由此，老茧便形成。

While calluses are generally useful, if the process continues unchecked a callus can thicken into a cone-shaped structure called a corn.

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，

These super calluses can be quite painful, and may require the attention of a doctor.

那样就会很疼，甚至需要去看医生。