One of my favorite ad tropes is the Body=Machine/Body=Factory idea, because the imagery is often more detailed and also more hilarious than in most ads. As a kid I used to LOVE any illustrations of the body that depicted tiny workers inside, such as The Human Body, for example. :D This link to a book about Fritz Kahn's Der Mensch als Industriepalastis also fascinating (although not advertisement). Brief video version of that book HERE (well worth 3 minutes of your time.) This series of articles and illustrations in the same vein (XD) appeared in the Berliner Morgenpost in 1931 and is simply breathtaking.
1933 Chinese Health Info Poster "The Human Body is Like a Factory"