SOVEREIGN, ISM / SCIENCE PHOTO LIBRARY SOVEREIGN, ISM / SCIENCE PHOTO LIBRARY
Lower spine. Frontal 3D CT (computed tomography) scan of a normal lower spine. At the base of the spine is the sacrum (bottom centre), which is a mass of five fused spinal bones (vertebrae). The sacrum articulates with the pelvic bones on either side. Ascending upwards from the sacrum are the five lumbar vertebrae (L5 at bottom, to L1 at top) with intervertebral discs (red) between them. The remaining vertebrae of the upper back and neck are not shown. The lumbar vertebrae are larger than the other vertebrae because they carry more weight. Either side of the vertebrae are vertebral processes, bony protrusions where the back muscles attach to the spine. The spine protects the spinal cord, and flexes to allow movement of the torso and neck.
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