Mark Hoofnagle (two posts in a row link to the same blog, weird) has an interesting answer to the question “Which parts of the human body could you design better?” His discussion of the female reproductive system brings up points I had never even thought to think of (if that makes any sense):
… pregnancy in humans results in a fetus sitting on the bladder and colon for several months …
Warning: there are scientific diagrams of human naughty bits in the article.