Unfortunately, all episodes of the ultimate guide (which might dissuade some for the thoughts associated between "ultimate" and monster truck rallies) are not listed on IMDb. This documentary series has captured my heart, and I believe the human body episode is the "best in". Featuring my favorite non-scientist commentator, he is eloquent, sincere, and impactive. In my hierarchy of best documentaries I've ever seen, I place Cosmos first, Moon Machines Second, and the entirety of Ultimate Guide a close and heartfelt 3.
Search out other episodes of The Ultimate Guide:
Birds of Prey Elephants Crocodiles Whales Elephants more.. but those are the best following the human body episode! ENJOY!