Yeah, if you look closely at the ground in the hell areas of Act 3, they're all covered in flesh. Like it's a thin layer, like walking on a drum or something. Which is gruesome, though kind of hard to figure how things like the tunnel worms can be under there, since it's just empty space below a thin layer of flesh.
But try not to trouble your pretty little head over that. I often wonder how the tunnel worms can pop up through the water caves in Act 2 without all the water draining down into their tubes.