Human Anatomy
Vertebral Column
Vertebral column for MBBS: regional vertebrae, curvatures, intervertebral discs and ligaments and disc prolapse, mapped to NMC codes AN50.1 to AN50.4.
MedNext Academy | 3 min read
Vertebral Column
Vertebral column for MBBS: regional vertebrae, curvatures, intervertebral discs and ligaments and disc prolapse, mapped to NMC codes AN50.1 to AN50.4.
The vertebral column chapter covers the regional vertebrae, the curvatures, the intervertebral discs and the ligaments that bind the spine. It underpins the anatomy of disc prolapse, the level at which the spinal cord ends and the cauda equina.
High-yield: Vertebral Column
- The vertebral column has thirty-three vertebrae: seven cervical, twelve thoracic, five lumbar, five fused sacral and four fused coccygeal.
- A typical vertebra has a body in front and a vertebral arch behind enclosing the vertebral foramen.
- The first cervical vertebra, the atlas, has no body and supports the skull.
- The second cervical vertebra, the axis, has the odontoid process around which the atlas rotates.
- The vertebral column has four curvatures: cervical and lumbar are secondary and convex forward, thoracic and sacral are primary and convex backward.
- The intervertebral discs lie between the vertebral bodies and act as shock absorbers.
- Each disc has a soft central nucleus pulposus and a tough outer anulus fibrosus.
- A prolapsed disc most often herniates posterolaterally, where the anulus is weak and the posterior longitudinal ligament is narrow.
- A prolapsed lumbar disc usually compresses the nerve root of the vertebra below the disc.
- The spinal cord ends at the lower border of the first lumbar vertebra in the adult.
- Below the cord the nerve roots continue as the cauda equina within the vertebral canal.
- The ligamentum flavum connects the laminae and is elastic, helping the column return to the upright.
- The anterior longitudinal ligament resists extension and the posterior longitudinal ligament resists flexion of the column.
- The nucleus pulposus is a remnant of the notochord, which explains its developmental origin.
Regions and key features
- **Cervical (seven):** Atlas and axis are specialised for head movement; foramina transversaria transmit the vertebral artery.
- **Thoracic (twelve):** Articulate with the ribs; primary curvature convex backward.
- **Lumbar (five):** Large bodies for weight bearing; common site of disc prolapse.
- **Intervertebral disc:** Nucleus pulposus within anulus fibrosus; herniates posterolaterally onto the nerve root.
NMC competencies in this chapter
- **AN50.1:** Typical and atypical vertebrae and regional differences
- **AN50.2:** Curvatures of the vertebral column and their significance
- **AN50.3:** Intervertebral discs, joints and ligaments of the column
- **AN50.4:** Applied anatomy of the vertebral column including disc prolapse
Frequently Asked Questions
Why does a prolapsed disc herniate posterolaterally?
The anulus fibrosus is thinnest behind and the posterior longitudinal ligament is narrow there, so the nucleus pulposus escapes to one side and presses on a nerve root.
Which nerve root does a lumbar disc prolapse compress?
A posterolateral lumbar disc usually spares the root exiting at its own level and compresses the root of the vertebra below, for example an L4 to L5 disc affects the L5 root.
Where does the spinal cord end?
In the adult it ends at the lower border of the first lumbar vertebra, below which the nerve roots continue as the cauda equina in the vertebral canal.
How does this chapter help in NEET-PG?
Disc prolapse, cord level and vertebral features are examined in orthopaedics, neurology and anaesthesia, so the vertebral column is directly high-yield for PG.
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