Topologically speaking, a human is a torus. Your digestive system is the hole in the doughnut.
Interestingly, this means in a two-dimensional world, an organism couldn't have a similar structure, since the digestive system would completely separate the animal into two halves.
Interestingly, this means in a two-dimensional world, an organism couldn't have a similar structure, since the digestive system would completely separate the animal into two halves.