The classic anatomy treatise is Gray's Anatomy, which includes awesome pictures. A 1918 edition of Gray's is posted on Bartleby.com (www.bartleby.com/107/). More recent editions are available in medical libraries and most online bookstores.
You can also get a lot of information from medical dictionaries (e.g., Steadman's or Gould). If that's not enough, The Attorney's Textbook of Medicine (a 14-volume set) has lots of information and pictures. Basic but accurate anatomical drawings are included in the American Jurisprudence 2nd Desk Book.
In addition, you can also find anatomical illustrations in FindLaw's Medical Demonstrative Evidence page and by following the links on General Medical Images.