Almost every creature in the game possesses a body (ghosts being a notable exception). These bodies are composed of bones, limbs, shells, hooves, hair, and many other pieces. Corpses can be cut up at a butcher's shop, yielding these parts as individual items, ready for whatever ghastly rite one may be planning. The stocks menu has a "Body parts" category that lists all such inedible parts, rotten or otherwise.
Also battles may cause a loss of a body part causing a total loss of it's function.