Explanation

Your spine runs through your back and it is what holds you up straight. It's like a tower made of blocks of bones, called vertebrae, one on top of another. It runs from your head to your bum, and attaches to your stomach and chest, and to your arms and legs. Your spine is not a perfectly straight line.

Even when you stand up straight, it bends in a little bit at the back of your stomach and out a little bit at your chest, but it does not bend sideways to the left or right.