Vertebral Column Notes

The Vertebral Column

General Characteristics

  • Extends from skull to pelvis.
  • Also called spine or spinal column (but not the spinal cord!).
  • Functions:
    • Transmits weight of the trunk to lower limbs.
    • Surrounds and protects the spinal cord.
    • Provides attachment points for ribs and muscles.
  • Flexible curved structure contains 26 irregular bones called vertebrae in five major regions.
    • 24 single bones.
    • 2 fused bones.

Regions and Curvatures

  • Regions: Approximately 28" long vertebral column broken into five major regions:
    • Cervical: consists of 7 vertebrae.
    • Thoracic: 12 vertebrae.
    • Lumbar: 5 vertebrae.
    • Mnemonic: Remember meal times: 7 am, 12 noon, and 5 pm.
    • Sacrum: one bone, formed from fusion of several bones, articulates with hip.
    • Coccyx: also fused bones that form terminus of column.

Curvatures

  • Four main curves help to increase resilience and flexibility of spine.
    • Cervical and lumbar curvatures:
      • Concave posteriorly.
    • Thoracic and sacral curvatures:
      • Convex posteriorly.

Structure of Vertebrae

  • All vertebrae have a common structural pattern consisting of:
    • Body: the anterior weight-bearing region.
    • Pedicles (2): short pillars that form sides of the vertebral arch.
    • Vertebral foramen: formed by the body and vertebral arch.
    • Intervertebral foramina: lateral openings between vertebrae for passage of spinal nerves.

Vertebral Processes

  • Vertebrae have seven processes:
    • Spinous process: projects posteriorly.
    • Transverse processes (2): project laterally.
    • Superior articular processes (2): protrude superiorly.
    • Inferior articular processes (2): protrude inferiorly.

Cervical Vertebrae

  • Distinguished by transverse and spinous processes.
  • C1 to C7: smallest, lightest vertebrae.
  • C3 to C7 share the following features:
    • Transverse foramen: found in each transverse process for artery passageways.
    • C7 is vertebra prominens; large and can be felt through skin, used as a landmark.

Atlas (C1)

  • No body or spinous process.
  • Superior surfaces of lateral masses articulate with occipital condyles.
  • Movement facilitates nodding head “Yes”.

Axis (C2)

  • Odontoid process (Dens) is a pivot point for rotation of atlas.
  • Dens is the “missing” body of atlas.
  • Movement allows side-to-side rotation for saying “No”.

Thoracic Vertebrae

  • T1 to T12 increase in size and articulate with ribs.
  • Unique characteristics:
    • Superior and inferior demifacets articulate with ribs.
    • T10 to T12 have only a single facet, not two.
    • Transverse processes have transverse costal facets that articulate with ribs (except T11, T12).

Lumbar Vertebrae

  • L1 to L5 “small of back”; receives most stress, so bodies are massive.
  • Large superior and inferior articulating processes.

Sacrum

  • Triangular bone shapes posterior wall of pelvis; made from five fused vertebrae (S1–S5).
  • Formed from fusion of the transverse processes.
  • Sacral promontory: anterosuperior margin of 1st sacral vertebrae.
  • Median sacral crest: roughened bumps on posterior midline due to fusion of spinous processes.
  • Sacral canal: continuation of vertebral canal.
  • Sacral hiatus: large opening at inferior end of canal for nerve passage.

Coccyx

  • Inferior bone formed from three to five fused vertebrae.
  • Articulates superiorly with sacrum.
  • Human "tailbone".