The lumbar region towards the base of the human spine takes the brunt of the range of forces involved in moving the body. Consequently, the lumbar vertebrae are the largest and strongest of the 33 in the human spine. The coloured x-ray, seen from the front, shows their broadly cylindrical shape. The sideways extensions (green) serve as muscle attachment points. Between the vertebrae lie softer discs made of cartilage (pink), while the spinal cord - the trunk route of the nervous system - lies in a canal that runs through the vertaebrae.