Now I am going to make the same thing a little more complicated. For instance, food that we say is inside your stomach is really on the outside of your body. It may be known as 'inside' the stomach, but in actual fact it is outside the stomach, just like the vase. Here we have a ball with a hole through it. If you say that it is a ball with a hole in it, you would be incorrect.
All surface area is outside the ball.
If you look at the sphere or ball, you can liken it to the human body. You will notice that one entrance to the hole is marked mouth and the other end is the anus. In between you have the esophagus, stomach, duodenum, small intestines and large intestines. It is the same with the lungs. What we call the inside of our lungs is in fact the outside of your body.