dorsum

dorsum (http://definr.com/dorsum)

     n 1: the posterior part of a human (or animal) body from the neck
          to the end of the spine; "his back was nicely tanned"
          [syn: back]
     2: the back of the body of a vertebrate or any analogous
        surface (as the upper or outer surface of an organ or
        appendage or part: "the dorsum of the foot")