Spinal Anatomy
Core concepts
Spinal anatomy integrates vertebrae, ligaments, cord, roots, and regional relationships. Know the 33 vertebrae: 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, and 3 to 5 coccygeal. A typical vertebra has a body, pedicles, laminae, transverse processes, spinous process, and vertebral foramen. Atypical features matter: C1 lacks a body and spinous process; C2 has the dens; C7 has a long spinous process; thoracic vertebrae have costal facets; lumbar vertebrae have large bodies and sagittal facets. Understand the anterior and posterior longitudinal ligaments, ligamentum flavum, facet capsular ligaments, and interspinous ligaments. The adult cord ends near L1-L2, the dural sac near S2, and the cauda equina fills the lower canal. Know intervertebral foramen boundaries and the rule that cervical roots exit above their corresponding vertebra, while thoracic and lumbar roots exit below.
Traps
Examiners mix up facet orientation by region: cervical facets are oblique, thoracic coronal, lumbar sagittal. They may ask which root exits at a given foramen. Do not confuse the conus medullaris with the dural sac. The spinal cord does not extend to the sacrum.
Worked example and rule of thumb
At C5-C6, the C6 root exits through that foramen, above the C6 vertebra. At L4-L5, the L5 root exits through that foramen, below the L4 vertebra. Rule: cervical root exits above its numbered vertebra; below the cervical region, the root exits below its numbered vertebra.
Exam focus
Vertebral levels, ligament function, facet orientation, and root exit are high-yield.