夏季如何迅速降温？(2)

A quick heads up here: Craig talks about temperatures using the Celsius scale. To get to Fahrenheit, multiply his number by 1.8. Then add 32.

这里快速提醒一下：克雷格谈论温度用的是摄氏度。要换算华氏温度，将摄氏度乘1.8，再加32，就好了。

Or you can just remember that when he says 37 degrees, that’s 98.6 Fahrenheit. And 40 Celsius is 104 Fahrenheit.

或者说，你可以记住，当他说37度时，其实是98.6华氏度。40摄氏度时，其实就是104华氏度。

Our body temperatures are regulated normally around 37 degrees. By the time we get to 40 degrees, we’re not functioning normally. We live very close to the edge.

我们的体温通常调节在37度左右。当体温达到40度时，身体就无法维持正常运作了。我们的生命也面临危险。

This is because we’re mammals—we’re warm-blooded. We’ve evolved to be good at maintaining a warm body temperature.

这是因为我们是哺乳动物——我们是温血动物(恒温动物)。我们经过进化，变得很擅长维持温暖的体温。

And most mammals have a nice blanket of insulating hair all over their bodies.

大多数哺乳动物全身都覆盖着一层隔离毛发的厚厚皮层。

Even people are covered with millions of hair follicles.

人类全身甚至也覆盖着数百万个毛囊。

The hairs are just a lot thinner and shorter than they are in other animals. Which means that when it comes to losing heat, we generally suck.

与其他动物相比，人类的毛发更稀疏，也更短。这也意味着，在散热方面，人类通常表现很糟糕。

Our bodies do, however, have a kind of emergency temperature relief valve. Craig has been studying it.

然而，我们的身体确实有一种紧急温度安全阀。克雷格一直在对此进行研究。

That valve is a special type of blood vessel.

这个安全阀是一种特殊血管。

This week it’s my turn to get stuck with the hard science word, so here goes: they’re called arteriovenous anastomoses.

这周轮到我来费劲解释这么难的科学术语了，它们叫做动静脉吻合血管。

Very nice.

不错。

Why thank you. I practiced. A lot. But let’s call them AVAs from now on.

谢谢。我练习过很多遍。但从现在起，我们把它们称作AVAs(动静脉吻合血管)吧。

Most arteries and veins connect through a bed of very thin capillaries that bring nutrients and oxygen to cells.

大多数动脉和静脉通过一层非常薄的毛细血管连接，毛细血管将营养物质和氧气带到细胞中。

AVAs, though, are different. They are direct junctions of arteries and veins, so blood flows through them pretty quickly.

然而，动静脉吻合血管则不同。它们直接连接动脉和静脉，因此，血液流经这些血管时速度会很快。

And the real key to their heat relief function is they are concentrated in just a few places in the body. Here’s Craig again:

这些散热功能的真正关键是，它们仅仅集中在身体的几个部位。以下是克雷格的观点:

We found that in the palm of the hand, the soles of the feet, and the upper part of the face, which are called non hairy skin, there are special blood vessels, and those blood vessels can shunt the blood from the arteries to the veins directly, bypassing the capillaries.

我们发现，在手掌、脚掌、脸的上部，也就是被称为无毛皮肤的部位，存在着特殊的血管，这些血管可以绕过毛细血管，将动脉血液直接分流至静脉。

You know mammals have fur. If you have fur you can't dissipate heat over your overall body surface very efficiently.

哺乳动物有皮毛。如果你也有皮毛，你就无法有效地散发全身体表的热量。

So mammals have these special blood vessels in their non hairy skin, the pads of their feet, the tongue, the ears in some cases.

哺乳动物的无毛皮肤处(脚掌肉垫、舌头、耳朵)也有这些特殊的血管。

To see if they could take advantage of AVAs in people, back in the early 2000s Craig and his colleague Dennis Grahn basically McGuyver’d this goofy device.

为了看看他们是否能利用人类身上的动静脉吻合血管，早在21世纪初，克雷格和他的同事丹尼斯·格兰恩发明了这个傻瓜式的设备。

They put a Plexiglass cylinder around someone’s hand and sealed it around their arm with part of a wetsuit sleeve.

他们将一个有机玻璃圆筒套在实验者的手上，然后用潜水服袖子将其封在手臂上。

Inside the cylinder, cool water ran over their palm.

圆筒内则有冷水流过他们的手掌。