The thoracic and sacral curvatures are primarily influenced by which spinal structure?

• A. Disc
• B. Vertebral Body
• C. Ligaments
• D. Nucleus Pulposus

Answer: (B)

The main factor shaping the thoracic and sacral curvatures is the geometry of the vertebral bodies themselves. These regions form the kyphotic primary curves because their vertebral bodies have shapes and alignments that produce a forward-bending profile from birth. Intervertebral discs mainly provide spacing and allow movement between vertebrae, but they don’t set the overall curve as the vertebral bodies do. The nucleus pulposus inside discs contributes to load distribution and motion, not the spine’s sagittal curve. Ligaments help stabilize and limit motion, but the primary curvature comes from the vertebral bodies’ shape and alignment.