I think I've said enough about that one.

我想关于这个我已经讲了够多了
Selective reabsorption happens in all

选择性重吸收则在所有的
other elements of the tubules,

其他肾小管的结构中发生
the proximal, the Loop of Henle, and the distal convoluted tubule.

近曲小管亨利氏环和远曲小管
How does selective reabsorption happen?

选择性重吸收如何作用呢
It happens by the physical processes of diffusion

它的原理是利用了扩散这一物理过程
or just the movement of molecules down concentration gradients,

或者说就是分子沿浓度梯度的运动规律
and it also happens by active transport.

同样也包括主动运输
We talked about active transport earlier.

我们前面说过主动运输了
We talked--for example when we were talking about the action potential,

我们谈到比如我们讲动作电位的时候
we talked about this active transport system

谈到过其中的主动运输系统
that's able to shuttle sodium and potassium molecules across membranes.

能够将钠和钾离子跨膜转运