Although precise boundaries between these three segments of bowel are not observed grossly or microscopically, there are histologic differences among duodenum, jejunum and ileum. <a href="http://www.vivo.colostate.edu/hbooks/pa">http://www.vivo.colostate.edu/hbooks/pa</a> ... atomy.htmlI am totally ready to believe that dogs have some sort of mechanism for avoiding being eaten alive by parasites, I would just like to see un-biaised proof of that.