The back is an intricate structure of bones, muscles, and other tissues that form the back, or posterior part of the body’s trunk, from the neck to the pelvis. At the center is the spinal column, which not only supports the upper body’s weight but houses and protects the spinal cord – the delicate nervous system structure that carries signals that control the body’s movements and convey its sensations. Stacked on top of one another are about 30 bones – the vertebrae – that form the spinal column, also known as the spine. Each of these bones contains a roundish hole that, when stacked in line with all the others, creates a channel that surrounds the spinal cord. The spinal cord descends from the base of the brain and extends (in the adult) to just below the rib cage.