Lower back bones. Close-up of the bones of the lower back from a female skeleton. The lower back is known as the lumbar spine & is made of bones called vertebrae. The lowest two lumbar vertebrae are seen at top and centre. At bottom centre is the sacrum. This is 5 fused vertebrae that attach the spine to the pelvic bone (seen at bottom right & bottom left). Between the vertebrae are Intervertebral discs made of cartilage. These cushion the vertebrae during running or jumping. The vertebrae are roughly cylindrical bones that support the body as well as encasing and protecting the spinal column.