and the levels of other key molecules at a constant level

和其它主要分子在每一天甚至一生中
throughout the day and throughout your life.

都维持在一个恒定的水平
It does that--and you're able to do that not by regulating

这维持了你能够维持内环境稳定
how much you eat of those things,

而不用去管你摄入了多少这些离子
but they kidney does that for you

是因为肾会通过监测体内这些离子的浓度
by sensing what concentrations are in your body,

在保留你所需的同时清除不需要的物质
keeping what you need and getting rid of what you don't need.

从而维持内环境的稳定
We started talking about

我们已经讨论过了
how the kidney is able to accomplish this remarkable task.

肾脏是如何完成这项艰巨任务的
Hopefully, the main point I wanted to make in the last lecture

我在上节课强调的就是
was how grateful you ought to be that your kidneys do function properly,

你们应该庆幸你们的肾脏在正常工作
because as one of the results of that is that

正因如此