In the sense that the inside of the digestive system is contiguous with the skin. You can trace a path from, say, the back of your knee, through the intestines

In the sense that the inside of the digestive system is contiguous with the skin. You can trace a path from, say, the back of your knee, through the intestines, and out to your eye lid, as you can trace a path from any point on a the outside of a torus. We're just a very complicated doughnut. It's something a medical scientist type I studied under was fond of saying, and I find it a useful model