The low ranks for WN reflect the ambiguity of definition of some of its classification subtrees.
for the 'body part' concept defined in Word-Net as "any part of an organism such as an organ or extremity" (which is not supposed to require domain-specific knowledge to identify) low scores were given (correctly) by judges to generic terms such as tissue, system, apparatus and process (process defined in WN as "a natural prolongation or projection from a part of an organism"), positioned in WN as direct hyponyms of body parts.