I had 2 questions regarding the giant tentacles that players encounter while traveling through Dead City.

• Where do they come from?
  
• Are they all coming from the same source?

Some are attached to sections of a broken bridge then to the ground. Some are inside the Hospital building, through walls. Big bloody w/ veins. I'm sure some of you know what I'm talking about. Parts of it reminds me of the movie Aliens, when the colonial marines are trying to locate civilian survivors. They pass through corridors covered with Xenomorph structure. Just before being attacked.

Those are from Doom3, which got them from Doom1, which got them from Aliens.

So yes, it should give you that feeling like in Aliens

In classic Doom they are literally just "guts," intestines and bones and such. In Doom3 they have more variety and are called just "unidentified growth" by Sgt. Kelly. In Rage, no one explains anything about them, and I think they are just there since Dead City puts alot of the Doom3 stuff there. It helps the area be very creepy and scary.

Edit: Oh and, when you're in the entrance of the building, when you fight the sludge-spitting mutant that has glowing parts, you can see that the stuff all over is actually like a "nest," like the mutant itself made all of it. Just like in Aliens, as well, you can see eggs in the slimy stuff, and these glow in the dark, awesome. I would guess the stuff in this area is made from some nasty chemicals and saliva and [censored] that comes from the mutant, holding together the bones of victims which are the base of the "nest" and you can see the bones if you look closely.

So, again, yes, it is supposed to feel like in Aliens, and that's where idSoftware originally got the idea to use the stuff. That is some classic idSoftware history
Aliens is what they based Doom on, and Rage borrows alot from Doom.