Vertebral Column: Regions, Curves, and Key Anatomy

The vertebral column (spine, backbone) runs from the skull to the tailbone and forms the core of the axial skeleton. Although vertebrae share a common blueprint, their shape and role change by region to balance mobility, protection, and load bearing.

This blog covers:

• How and why we divide the spine into regions

• Normal spinal curves and what goes wrong

• The basic vertebra “template” (body, arch, processes)

• Regional anatomy: cervical, thoracic, lumbar, sacrum, coccyx

Regions of the Spine (Count & Function)

Region	Typical Count	Curve (adult)	Primary Role
Cervical	7 (C1–C7)	Lordosis	Head/neck mobility; vertebral artery passage
Thoracic	12 (T1–T12)	Kyphosis	Rib articulation; thoracic protection
Lumbar	5 (L1–L5)	Lordosis	Weight bearing and trunk motion
Sacrum	5 fused	Kyphosis	Pelvic stability; load transfer
Coccyx	3–5 fused (avg 4)	—	Ligament/muscle attachment (tailbone)

Total: ~33 vertebrae (variable due to coccyx)

Why the Spine Has Curves

Primary (fetal) curves

• Thoracic kyphosis and sacral kyphosis develop in utero and persist into adulthood.

Secondary (postnatal) curves

• Cervical lordosis forms as infants lift and hold the head (≈3–4 months) and sit (≈9 months).

• Lumbar lordosis develops as children stand and walk (≈12–18 months).

When curves go wrong

• Hyperkyphosis (exaggerated thoracic curve): rounded upper back, pain, stiffness.

• Hyperlordosis (exaggerated cervical/lumbar curve): deep inward arch, low-back pain, muscle imbalance.

• Scoliosis: lateral curvature with vertebral rotation/wedging visible on frontal radiograph.

Curvatures help distribute load, improve shock absorption, and enable upright posture. Exaggerations are often linked to posture, muscular imbalance, or bone weakness.

The Basic Vertebra Blueprint

Most vertebrae share three elements:

1. Vertebral body

   • Superior/inferior endplates articulate with intervertebral discs.

   • Annular epiphysis: peripheral ring with a secondary ossification center.

2. Vertebral arch

   • Pedicles (anterior arch segments) connect the body to the arch.

   • Laminae (posterior arch segments) meet at the midline.

   • Vertebral foramen: central canal bordered by body and arch. Stacked foramina form the vertebral canal.

3. Processes

   • Spinous process: posterior projection (palpable on the back).

   • Transverse processes: lateral projections.

   • Articular processes (superior & inferior) form synovial zygapophyseal joints between adjacent vertebrae.

Key spaces & contents

• Vertebral canal: spinal cord, meninges, vessels (anterior/posterior spinal arteries, venous plexus), ligaments (ligamenta flava, posterior longitudinal ligament).

• Intervertebral foramen: exits for spinal nerve roots.

• Intervertebral discs: fibrocartilaginous shock absorbers that allow flexibility.

Regional Anatomy and Distinctive Features

Cervical Spine (C1–C7)

• Function: high mobility; passage for vertebral arteries.

• General traits (C3–C7):

  • Transverse foramen in each transverse process for the vertebral artery (usually C6–C1).

  • Bifid spinous processes (commonly C2–C6) for increased muscle/ligament attachment.

  • Articular facets oriented to favor rotation and flexion-extension.

Special vertebrae:

• C1 (Atlas):

  • No body; anterior and posterior arches with lateral masses.

  • Superior articular facets receive occipital condyles (atlanto-occipital joint: nodding “yes”).

  • Posterior tubercle (instead of a true spinous process).

  • Groove for vertebral artery curves over the posterior arch.

• C2 (Axis):

  • Dens (odontoid process) projects superiorly and articulates with the atlas and transverse ligament.

  • Dens is the embryologic remnant of the atlas body (fused during development).

  • Atlanto-axial joint allows rotation (“no”).

Clinical note (C6): prominent carotid tubercle on the anterior transverse process; the common carotid artery can be compressed here.

Thoracic Spine (T1–T12)

• Function: rib articulation; thoracic cage protection; limited motion.

• General traits (typical T2–T9):

  • Costal facets on vertebral bodies (superior/inferior demi-facets) for rib heads.

  • Transverse costal facets for rib tubercles.

  • Longer, inferior-slanting spinous processes.

Atypical thoracics:

• T1: single full facet for rib 1 head + inferior demi-facet for rib 2; resembles lower cervical morphology.

• T10: single full facet (no inferior demi-facet).

• T11–T12: single full facet on the body; transverse facet rudimentary/absent (no rib tubercle articulation).

Lumbar Spine (L1–L5)

• Function: major weight bearing; flexion/extension with limited rotation.

• Traits:

  • Large, kidney-shaped bodies.

  • Short, broad spinous processes (quadrate in profile).

  • Costal processes (embryologic rib remnants) rather than true transverse processes.

  • Facet orientation favors flexion/extension and resists rotation.

Sacrum and Coccyx

• Sacrum (5 fused): wedge-shaped; forms posterior pelvis.

  • Base (superior) with sacral promontory (part of pelvic brim).

  • Ala (wings) laterally; auricular surfaces articulate with the ilia at the sacroiliac joints.

  • Sacral canal continues from vertebral canal; opens at sacral hiatus (transmits S5 and coccygeal nerves).

  • Anterior/posterior sacral foramina for anterior/posterior rami of sacral nerves.

  • Median, medial, and lateral sacral crests from fused processes; sacral cornua border the hiatus.

• Coccyx (3–5 fused; avg 4): small tailbone; coccygeal cornua project cranially; important for ligament and pelvic floor muscle attachments.

Quick “Spot the Differences” Table (C/T/L)

Feature	Cervical	Thoracic	Lumbar
Body	Small; rectangular	Heart-shaped	Large; kidney-shaped
Foramina	Transverse foramina present	None	None
Spinous process	Often bifid (C2–C6)	Long, slanted inferiorly	Short, broad, quadrate
Costal facets	No (atlas/axis special)	Yes (rib head & tubercle)	No
Transverse process	Foramen + anterior/posterior tubercles	Articulates with rib (typical)	Costal processes (rib remnants)
Motion bias	Flex/extend, rotate	Rotation limited by ribs	Flex/extend; resist rotation

Ligaments & Stabilizers

• Anterior longitudinal ligament (ALL): anterior bodies; limits extension.

• Posterior longitudinal ligament (PLL): posterior bodies/canal; limits flexion.

• Ligamenta flava: lamina-to-lamina; elastic recoil in extension.

• Interspinous/supraspinous: between/over spinous processes; limit flexion.

• Nuchal ligament: cervical region continuation of supraspinous, supports head posture.

• Facet capsules: stabilize zygapophyseal joints.

Many back pain syndromes involve these ligamentous structures or the disc-facet complex.

Clinical Corner

• Disc herniation: most frequent in lumbar region; compresses exiting/descending nerve roots causing radicular pain.

• Cervical pathology: may involve vertebral artery (through transverse foramina) or cord compression due to narrow canal.

• Scoliosis screening: look for lateral curvature and rib hump (vertebral rotation).

• Hyperkyphosis/hyperlordosis: often postural; evaluate muscle balance, bone health.

Study Checklist

• Memorize counts (7C, 12T, 5L, 5 fused S, 3–5 fused Co).

• Know which curves are primary vs secondary.

• Recognize atlas (no body), axis (dens), thoracic costal facets, lumbar costal processes.

• Understand what travels in the vertebral canal and through intervertebral foramina.

• Be able to identify a vertebra’s region from a single specimen.

Mini-Quiz (5 quick checks)

1. Which curves are primary and present in the fetus?

2. What unique feature runs through cervical transverse processes?

3. Which thoracic vertebrae typically have single full facets on the body?

4. What limits the depth of a bird’s-mouth style notch in a rafter—kidding—What limits lumbar rotation?

5. What exits the intervertebral foramen?

Answers:

1. Thoracic and sacral kyphoses.

2. Vertebral artery (C6–C1) and accompanying veins.

3. T10–T12 (T11–T12 also lack meaningful transverse facets).

4. Facet orientation and robust interlocking in the lumbar spine.

5. Spinal nerve roots (mixed spinal nerve) with vessels.