What are these lines?

So I am redoing some brake lines. Gotta love Ontario! Anyways while I was in there I noticed these two lines. They go from metal lines into plastic and up into the engine bay. In the engine bay the plastic lines lead to what looks like two breathers? Not sure where they come from and what fluid they are for? This is on the front drivers side wheel well.

The metal line looks pretty crusty just before where it enters the plastic line. So I would like to replace it before it becomes a problem. Thanks for any help!!!

https://ibb.co/RTFzh4N

https://ibb.co/vBdGXMw

 

I believe they are for the transfer case? Its really hard to see where they lead to under the vehicle.

 

I think you're right.
This might help, although it's a 2014...

Breather line location guide | Toyota Tundra Forum (tundras.com)