Photograph of the human first lumbar vertebra (L1), one of five bones that comprise the lumbar spine of the lower back. The vertebra is seen in anterior aspect with superior surface at bottom: in other words, one is looking at the front of the bone with its anatomical upper surface at bottom. Lumbar vertebrae have large, wide bodies - the cylindrical bone at front; the bony, transverse processes (protruding to left and right) are relatively short and thickened in L1. The lumbar vertebrae are the largest of the unfused vertebrae in the backbone.