There are also perfectly acceptable biology texts that use such models. Example: illustrations portraying the various stages of human development from birth thru adolescence/ adulthood. Very useful when giving "the talk" -- I wish such books & diagrams were available I was a pre-teen and wondering just what the heck was going on with my suddenly changing anatomy. But unfortunately, this is also the sort of thing that appeals to the perverts, which is a sad commentary on society. (By that I mean human society, not singling any particular nation/ethnic/religious/whatever group out.)