什么是汗水？

　　Your body works best when its temperature is about 37? Celsius. When your body gets hotter than that, your brain doesn't like it — it wants your body to stay cool. So the part of your brain that controls temperature, called the hypothalamus, sends a message to your body, telling it to sweat.

　　人体体温在37摄氏度时，身体各功能活动最佳。当体温超过这个温度时，大脑就不乐意了，它要让体温降下来。所以大脑中控制体温的部分下丘脑就会发出一个信号给身体，告诉它要排汗。

　　Then special glands in your skin called sweat glands start making sweat. Sweat is also known as perspiration, and it is made almost completely of water, with tiny amounts of other chemicals like ammonia, urea, salts, and sugar.

　　人体皮肤中有种特别的腺体叫汗腺，负责分泌汗液。汗液几乎全是由水组成，也含有微量的化学元素，包括氨、尿素、盐和糖。

　　The sweat leaves your skin through tiny holes called pores. When the sweat hits the air, the air makes it evaporate. As the sweat evaporates off your skin, you cool down.

　　汗液通过皮肤上的小孔即毛孔排放出来。当汗液和空气接触之后，就会蒸发。汗水一旦蒸发，人体的体温就会降下来。

　　Sweat is a great cooling system, but if you're sweating a lot on a hot day, you could be losing too much water. Then you need to put liquid back in your body by drinking plenty of water so you won't get dehydrated.

　　出汗是很好的降温系统。但是，如果你在天热的时候出了很多汗，你就可能流失过多的水分。这时，你就需要通过大量喝水来补充体内水分，不然你就会脱水。

　　Why does sweat smell? Sweat by itself doesn't smell at all. It's the bacteria that live on your skin that mix with the sweat and give it a stinky smell. And when a person reaches puberty, special hormones affect the glands in the armpits — these glands make sweat that can really smell.

　　那么，汗水为什么会有味道呢？汗水本身是没有味道的。但皮肤中的细菌和汗水结合起来就会产生一种臭味。当人到了青春期之后，就会在腋窝的汗腺中产生一种特殊的激素，使得汗水闻起来有种汗臭味。

　　词汇点津：

　　sweat glands 汗腺