Vertebral Column: Cervical, Thoracic, and Lumbar Anatomy With Clinical Correlations

The vertebral column comprises 33 vertebrae in five regions: 7 cervical, 12 thoracic, 5 lumbar, 5 fused sacral, and 4 (variable) fused coccygeal. Three sagittal curves develop during ontogeny: cervical lordosis and lumbar lordosis (secondary curves, develop after birth as the infant lifts the head and stands), and thoracic kyphosis and sacral kyphosis (primary curves, retained from the embryonic flexed position). Region-specific vertebral morphology reflects the loads each region carries. Cervical vertebrae are small, mobile, and feature transverse foramina (containing the vertebral artery in C1-C6). Thoracic vertebrae are intermediate-sized with facets for rib articulation (costal facets). Lumbar vertebrae are large with thick bodies and short, blocky spinous processes to support body weight. Sacral vertebrae are fused into a single sacrum that transmits forces to the pelvis via the sacroiliac joints. Region-specific features matter clinically because they dictate where pathology localizes and how it presents.

The cervical region has three special vertebrae and four typical ones. C1 (ATLAS) has no body and no spinous process — it is a ring with lateral masses that articulate with the occipital condyles above (atlanto-occipital joint, allows yes-nodding flexion-extension) and with C2 below. C2 (AXIS) has the ODONTOID PROCESS (dens) projecting upward, around which C1 rotates (atlantoaxial joint, allows no-shaking rotation; about 50% of total cervical rotation). The transverse ligament holds the dens against C1, and its rupture (from trauma or rheumatoid arthritis) causes atlantoaxial instability. C2 has a bifid (split) spinous process — a feature shared by C3-C5. C7 (VERTEBRA PROMINENS) has the longest spinous process, easily palpable at the base of the neck. C3-C6 have transverse foramina containing the vertebral artery; C7\u2019s transverse foramen typically contains only the vertebral vein. Cervical disc herniations most commonly occur at C5-C6 and C6-C7, producing C6 or C7 radiculopathy respectively.

Thoracic vertebrae T1-T12 each articulate with at least one pair of ribs. Most have superior and inferior costal facets on the body (articulating with rib head) plus transverse costal facets (articulating with rib tubercle). T1, T11, and T12 are atypical: T1 has a complete superior facet for the first rib (and a half facet for rib 2); T11 and T12 have single facets and lack transverse costal facets (because ribs 11 and 12 are floating). The thoracic spine is the LEAST mobile region because of (a) thinner intervertebral discs, (b) the splinting effect of the rib cage, and (c) downward-pointing spinous processes that limit extension. Disc herniations are uncommon in the thoracic spine but when they occur they can cause myelopathy (cord compression) more readily than in cervical or lumbar regions because the cord occupies more of the canal at thoracic levels with less buffer.

Lumbar vertebrae have large, kidney-shaped bodies to bear weight, short blocky spinous processes for paraspinal muscle attachment, and facet joints oriented in the sagittal plane (allowing flexion-extension but restricting rotation). The L4 spinous process is at the level of the iliac crest — the surface landmark used for lumbar puncture (the L3-L4 or L4-L5 interspace, safely below the conus medullaris which ends at L1-L2 in adults). The L5-S1 joint transmits the entire upper body weight to the sacrum and is the most common site of spondylolisthesis. The SACROILIAC (SI) JOINT is a strong, partially synovial articulation between the sacrum and ilium that transmits force from spine to lower extremity; SI joint dysfunction causes posterior buttock pain that can mimic lumbar radiculopathy and is provoked by FABER and FABRE tests on exam. Lumbar disc herniations are most common at L4-L5 and L5-S1, producing L5 or S1 radiculopathy respectively.

A critical anatomic rule: in the CERVICAL spine, nerve roots exit ABOVE the same-numbered pedicle (C5 exits between C4 and C5). Because there are 7 cervical vertebrae and 8 cervical nerve roots, the C8 root exits between C7 and T1, and from T1 onward roots exit BELOW the same-numbered pedicle. A POSTEROLATERAL (paracentral) disc herniation typically impinges on the traversing nerve root that exits BELOW the level. So a C5-C6 posterolateral herniation pinches the C6 root (which exits at C5-C6); an L4-L5 posterolateral herniation pinches the L5 root (which traverses past L4-L5 to exit at L5-S1). A FAR LATERAL (foraminal) disc herniation pinches the EXITING nerve root at the level of the disc, NOT the traversing one. This explains why exam patterns are level-specific and predictable.

Three common degenerative cord/root pathologies present differently. SPINAL STENOSIS (most often lumbar) is canal narrowing from a combination of hypertrophic facets, ligamentum flavum thickening, and disc bulge; patients have NEUROGENIC CLAUDICATION — bilateral leg pain and weakness with walking, RELIEVED BY LUMBAR FLEXION (forward bending opens the canal, hence the “grocery cart sign” of leaning on the cart). DISC HERNIATION presents acutely or subacutely with unilateral, dermatomal radicular pain made WORSE by sitting and the Valsalva maneuver, and reproducible with straight leg raise. FACET ARTHROPATHY produces localized axial back pain worse with extension and rotation, often without true radicular signs; medial branch nerve blocks can both diagnose and treat. Distinguishing them at the bedside avoids unnecessary surgery — and patient counseling depends on the diagnosis.

Describe the back pain pattern, radicular distribution, and provocative maneuvers and AnatomyIQ ranks the most likely level and pathology (disc herniation vs stenosis vs facet vs SI joint vs muscular). Upload an MRI and the overlay identifies the vertebral level, disc spaces, nerve roots, and ligamentum flavum, with severity grading for stenosis and herniation. This content is for educational purposes only.