I just stumbed across these images of amazing knitted innards at the Sarah Illenberger website. This site is mainly in German, so I am unsure if she knit or photographed these pieces, but I love how the mohair yarn has captured the feel of the pieces.
Brain Embroidery at Monster Crochet
Knitted Digestive System at Craftster
Other Fiber Brains at Museum of Fabric Brain Art
Womb at Knitty