Duodenum
Guts?
jejunum
caecum
I think I’ll name this part right there “Bob”.
Islets of Langerhans
appendix
sigmoid flexure
Asshole.
ETA: that was a reply to the OP, not a comment directed at eschereal!
Hey!
No, no, an answer! My post was an answer!
One of the more disturbing things I’ve recently run across: Toxic Megacolon.
Rectum
(Make all the shitty jokes you want!) 
Rumen
(we’re not limited to humans, right?)
Aaaaanus.
Ileum
Crypt of Lieberkühn