两个as是同一个意思，都是“正如”的意思，词性上属于连词。

通常as作连词时后面接句子：

David, as you know, has not been well lately。

As Napoleon once said, attack is the best method of defence.

但是，当as从句中的主语与主句主语一致并且as从句中的谓语为be动词时，那么as从句中的主语谓语都可以省略。如果be后面还有与主句相同的部分，还可继续省略，你的句子就是这种情况。完整的说法是：

The noun 'descent' is sometimes used figuratively,　as （it is used） in the text, and as （it is used） here.

这种省略结构也存在与if, though, when, while从句中，如：

While (he was) at high school, John played football a lot.

If (it is) used carefully, the mobile phone can last at least 5 years.

Though (he is) tired, Mark doesn't want to give up.