Lumbar spine and pelvis. Computerenhanced Xray of the healthy lumbar spine (lower back) and pelvis of a human. At top can be seen the lower ribs of the ribcage. The 12th thoracic vertebra (top centre) supports the lower 12th rib. Below it are the five lumbar vertebrae (L1 to L5, coloured green and pink). L5 (at centre) attaches to the sacrum (pink), five fused vertebrae. On either side of the sacrum are the pelvic bones (green bluepink), two hipbones which curve around and meet at the front. At lower left and right are the thighbones of the legs which articulate with the pelvis. The pelvis supports organs of the abdomen, while the spine supports the body and spinal cord.