Bones, muscles, and other tissues make up the structure that forms the back. The spinal column, in the middle, supports the weight of the upper body and also acts as a protective conduit for the spinal cord – the nervous system that controls the body’s movements and transmits sensations. The spinal column (or spine) comprises about 30 vertebrae, which are small bones arranged one on top of another, through which the spinal cord runs.

Sponge-like pads of cartilage between the vertebrae enable the back to be flexible and also cushion the stress on the bones when the body moves. The vertebrae are held in place by ligaments and tendons attach the muscles to the spinal column.