Zygote builds them as a seperate body part. Actually, it is part of the figure hierarchy, so they are part of about a dozen body parts. Only uber expensive programs can handle obj files with a hierarchy, so they grossly simplify it before they UV map it. Zygote accidently shipped the nude asian female and nude black female figures with the full hierarchy. It didn't work very well as a Poser figure but it was fairly interesting to poke through it, before they fixed it and sent me the new one.