HLTH1008 Chap.9 Vertebral Column, Back Muscles and Spinal Movement
Vertebral Column, Back Muscles and Spinal Movement
The vertebral column combines strength with movement. This chapter explains why a lumbar disc herniates posterolaterally onto a spinal nerve, then sets out the curvatures, the ligaments of the column and the two-stage whiplash injury. It covers the atypical vertebrae, the atlas and axis, the craniovertebral joints and their ligaments, and the ranges of cervical movement.
It works a facet mechanics example for lumbar rotation and finishes with the extrinsic and intrinsic back muscles and the suboccipital region. Movement ranges are given as the workshop answers state them, including where two values for the same joint differ. The extrinsic back muscles also connect this chapter to the shoulder.
What this chapter covers
- 01
Intervertebral disc structure and prolapse
- 02
Curvatures, lordosis, kyphosis and scoliosis
- 03
Anterior and posterior longitudinal ligaments
- 04
Ligamentum flavum and the posterior ligaments
- 05
Atlas, axis and craniovertebral joints
- 06
Facet orientation and spinal movement
- 07
Extrinsic back muscles
- 08
Intrinsic back muscles and the suboccipital region
Worked example · free
Choosing the ligament that limits a movement
- +1The anterior longitudinal ligament runs down the front of the vertebral bodies and discs from the axis to the sacrum.
- +1The workshop answers describe it as the only ligament that limits extension, so it is stretched or torn.
- +1The ligamentum flavum joins adjacent laminae and forms part of the back of the canal.
- +1In forceful hyperextension it can buckle forward and compress the cord and nerves.
Key terms
- Annulus fibrosus
- The layered outer ring of an intervertebral disc.
- Nucleus pulposus
- The gel-like centre of an intervertebral disc.
- Ligamentum flavum
- The paired elastic ligament between adjacent vertebral laminae.
- Zygapophyseal joint
- A plane synovial joint between vertebral articular processes.
- Alar ligaments
- Cords from the dens to the occipital condyles that check rotation.
- Erector spinae
- The intermediate back muscle group of iliocostalis, longissimus and spinalis.
- Kyphosis
- An exaggerated posterior convexity of the thoracic curve.
- Anterior longitudinal ligament
- The broad ligament on the front of the vertebral bodies that limits extension.
- Spinal canal stenosis
- Abnormal narrowing of the vertebral canal that can compress the cord or nerves.
- Atlas
- The first cervical vertebra, which carries the skull and pivots around the dens.
Vertebral Column, Back Muscles and Spinal Movement FAQ
Why do lumbar discs herniate posterolaterally?
At the back the annulus fibrosus has fewer, thinner lamellae, so the nucleus pulposus sits posteriorly and escapes posterolaterally through a degenerate annulus. Spinal nerves leave the intervertebral foramen just there, so the herniation compresses a nerve and pain follows its distribution.
Which segment of the neck rotates most?
The atlanto-axial joint between C1 and C2 is the most mobile segment of the spine, and its movement is mainly rotation. The workshop answers give its rotation as 40 to 45° in one place and about 50 to 90° in another, while the atlanto-occipital joints mainly allow nodding.
What does the transverse ligament of the atlas do?
It holds the dens against the anterior arch of the atlas and forms part of the cruciform ligament. If it ruptures or is lax, as in about 20% of people with Down syndrome, atlanto-axial subluxation can compress the spinal cord.
What happens in a whiplash injury?
The workshop answers describe two stages. The neck is first thrown into hyperextension, stretching or tearing the anterior longitudinal ligament, and then rebounds into hyperflexion, when the facets can jump. A full answer names both phases and the ligament involved.
Why does the lumbar spine rotate so little?
Its facet joints face mainly sagittally, which blocks axial rotation to about 1 to 3° per segment. Horizontal facets, as at the top of the neck, allow rotation, while vertical facets prevent it, so facet orientation is the first reason to give.
Exam move
Draw a lumbar disc from above with the thick front and thin back of the annulus, then add the spinal nerve beside it. Learn the spinal ligaments as a list of course, attachments and role. For the upper neck, label the atlas and axis on a model and say the joints and ligaments aloud. Finish by working the lumbar rotation example in both directions and listing the back muscles layer by layer.
Add the extrinsic back muscles with their nerves, especially trapezius with the accessory nerve and latissimus dorsi with the thoracodorsal nerve, since they link this chapter to the shoulder.
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