I say Tongue because if it was the Intestines it would have to go from the lower half of your body all the way upwards. Plus it looks more like a Tongue. Usually I just say Tentacle so I don't enter a Debate in the game with a nerd.

Now if we look at this body here we can see where the intestines are. Now the End at the bottom there would have to some how make it's way back up to it's mouth. The only way I can imagine this is if...the Intestine went inside to the stomach up the esophagus or whatever it's called up to the throat. However the Intestines are extremely long, In theory the intestines can stretch out around the world. (( Makes you wonder how the devil we have all that in us. )) I don't believe the Smoker changes like that though.
The only theory I can imagine is if the Intestine Merges with the Tongue which hints why it can go so far. Either that or the Tongue just mutates to be so long. (( Hey if the Witch can be so deadly and not look like it, or the Tank be so dang big, why not this? ))
But then again, I dunno much, if anything about Biology.