The topological human

You know, we are not simple beings in a topological sense. We have a hole down the middle-- called a "handle" in topology-- like a piece of macaroni. In a topological sense, your food, gorge, and feces are not inside of you; they are outside. The gut is a specialized fly-by zone for these items to interact with the porous "skin" called the intestinal wall.

The image gets weirder. How small does a body opening have to be to constitute a closed surface? If your urethra is a true opening, then the contents of your bladder are also topologically outside the body. If the vagina and cervix are openings, then a fetus develops topologically outside the mother's body.

What is inside and outside of you? Where is the surface of your body? Humans, and indeed all objects, have rather fuzzy edges, eh?