Illustration of the lumbar (lower) spine. The spinal column is made up of vertebrae, block-like bones that protect the spinal cord and support the upper body. The projections from the vertebrae are the attachment sites for muscles. The spaces between the blocks of the vertebrae hold intervertebral discs (grey), which cushion the spine against shock and allow a degree of flexibility. At the base of the spine is the sacrum, which forms the rear of the pelvis.