【英语时差8,16】嘴唇为何会干？

 Let’s start by reviewing the ways in which the surface of our lips is different from the surface of the skin on the rest of our bodies. Basically, our lips are made of the same mucus membrane¹ that coats the inside of our mouths. This means two things. First, our lips don’t have the same protective outer layer as the skin elsewhere on our bodies. This layer is part of the barrier to evaporation², and its absence means our lip skin retains less fluid. Second, our lips don’t have the same glands³ and pigments⁵ as ordinary skin. For example, lips don’t have oil glands, which also help keep moisture from evaporating, and they contain less melanin, the pigment⁴ that helps protect our skin from sunburn.

1 membrane   

n.薄膜，膜皮，羊皮纸

参考例句：

• A vibrating membrane in the ear helps to convey sounds to the brain.耳膜的振动帮助声音传送到大脑。
• A plastic membrane serves as selective diffusion barrier.一层塑料薄膜起着选择性渗透屏障的作用。

2 evaporation   

n.蒸发，消失

参考例句：

• Be careful not to lose too much liquid by evaporation.小心不要因蒸发失去太多水分。
• Our bodies can sweat,thereby losing heat by evaporation.我们的身体能出汗，由此可以蒸发散热。

3 glands   

n.腺( gland的名词复数 )

参考例句：

• a snake's poison glands 蛇的毒腺
• the sebaceous glands in the skin 皮脂腺

4 pigment   

n.天然色素，干粉颜料

参考例句：

• The Romans used natural pigments on their fabrics and walls.古罗马人在织物和墙壁上使用天然颜料。
• Who thought he might know what the skin pigment phenomenon meant.他自认为可能知道皮肤色素出现这种现象到底是怎么回事。

5 pigments   

n.（粉状）颜料( pigment的名词复数 )；天然色素

参考例句：

• The Romans used natural pigments on their fabrics and walls. 古罗马人在织物和墙壁上使用天然颜料。 来自辞典例句
• The original white lead pigments have oxidized and turned black. 最初的白色铅质颜料氧化后变成了黑色。 来自辞典例句