Vertebral Column Anatomy
Overview
The vertebral column consists of 33 vertebrae (7 cervical + 12 thoracic + 5 lumbar + 5 fused sacral + 4 coccygeal). It houses the spinal cord, acts as the central axial scaffold, and absorbs compressive loads through intervertebral discs.
Regional Distinctions
- Cervical (C1-C7): Transverse foramina housing the vertebral arteries. C1 (Atlas) has no vertebral body. C2 (Axis) has the odontoid process. C3-C7 have bifid spinous processes.
- Thoracic (T1-T12): Costal facets for rib articulation. Long, inferiorly angulated spinous processes (overlap the level below on lateral view).
- Lumbar (L1-L5): Large, kidney-shaped vertebral bodies designed for maximal weight-bearing. Short, horizontal 'Scottie dog' transverse processes.
Ligamentous Stabilisers
- Anterior Longitudinal Ligament (ALL): Resists hyperextension. Primary stabiliser disrupted in extension injuries (e.g., whiplash).
- Posterior Longitudinal Ligament (PLL): Thin centrally. Resists hyperflexion. Its central weakness explains why disc herniations preferentially occur posterolaterally.
- Ligamentum Flavum: High elastin content (yellow). Connects adjacent laminae. Can hypertrophy and ossify, contributing to central canal stenosis.
- Supraspinous Ligament: Connects spinous process tips. Disrupted in 'chance' flexion-distraction fractures.
WarningDisc Herniation: Which Root is Compressed?
At the lumbar level, nerve roots exit BELOW the same-numbered pedicle. A postero-lateral L4/L5 disc herniation (the most common) compresses the traversing L5 root (which is passing through the canal on its way down to exit at L5/S1). A far-lateral (foraminal) herniation compresses the exiting L4 root.
High Yield Facts
LightbulbFRCR / MD Prep Pearl
Conus medullaris normally ends at L1-L2 in adults (lower in childhood). Cauda equina begins below L2. Safe LP space is L3/L4 or L4/L5. Artery of Adamkiewicz (of Haller) — the dominant thoracolumbar feeder of the anterior spinal artery — usually arises from T8-L2 on the left side.