Anatomy of the Spine

Objectives

• Distinguish and describe the cervical, thoracic, lumbar, sacral, and coccygeal vertebrae.
• Describe the vertebral curvatures.
• Describe movements in each vertebral column region.
• List structures connecting adjacent vertebrae.
• Identify ligaments of the intervertebral joints.

Overview of Vertebral Column

• Extends from skull to pelvis, supporting the body and protecting the spinal cord.
• Consists of 33 vertebrae:
  • 24 single vertebrae
  • Sacrum (5 fused vertebrae)
  • Coccyx (4 fused vertebrae)
• Breakdown of single vertebrae:
  • 7 Cervical
  • 12 Thoracic
  • 5 Lumbar

Intervertebral Discs

• Separate single vertebrae with fibrocartilage pads.
• Cushion vertebrae and absorb shocks.
• Support flexible body trunk.
• Primary curvatures (thoracic and sacral) present at birth.
• Secondary curvatures (cervical and lumbar) develop with growth.

Typical Vertebra Structure

• Comprised of a body (centrum) and arch.
• Vertebral arch includes:
  • 2 Pedicles
  • 2 Laminae
• Vertebral foramen houses the spinal cord.
• Processes:
  • 1 Spinous process
  • 2 Superior and 2 Inferior articular processes
  • 2 Transverse processes

Cervical Vertebrae

• 7 cervical vertebrae (C1-C7) form the neck.
• Atlas (C1) allows nodding "yes"; lacks a body, supports the skull.
• Axis (C2) allows head rotation "no"; features the odontoid process (dens).
• Typical cervical vertebrae (C3-C6) are small, with short, bifid spinous processes.
• C7 notable for its long, non-bifid spinous process.

Movements at Joints

• Atlanto-occipital joint: Flexion, extension, lateral flexion (no rotation).
• Atlanto-axial joint: Extensive rotation (to say "no").

Thoracic Vertebrae

• 12 vertebrae (T1-T12) are typical and larger than cervical.
• Heart-shaped bodies with costal demifacets for rib articulation.
• Long, downward-hooking spinous processes.

Lumbar Vertebrae

• 5 vertebrae (L1-L5) are massive, block-like.
• Short, hatchet-shaped spinous processes.
• Solid structure supports extensive movements like flexion, extension, lateral flexion, and rotation (less extensive in the lumbar region).

Sacrum

• Formed by 5 fused vertebrae.
• Upper articulation with L5; lower with coccyx.
• Forms posterior pelvic wall.
• Features sacral promontory and sacroiliac joints.
• Sacral canal continues as sacral hiatus.

Coccyx

• Formed by the fusion of 4 small vertebrae.

Intervertebral Joints

• Include discs with annulus fibrosus (fibrocartilage) and nucleus pulposus (gelatinous core).
• Allow flexion, extension, and shock absorption.
• Ligaments:
  • Anterior and Posterior longitudinal: along vertebral bodies.
  • Supraspinous, Interspinous, Ligamentum Flavum, Intertransverse ligaments connect adjacent vertebrae.
• Ligamentum Nuchae: thickened supraspinous and interspinous ligaments in cervical region.

Conclusion

• Anatomy and functioning of the spine are integral to support and movement.
• Various vertebrae and ligaments contribute to the complex structure and flexibility of the vertebral column.