Lecture 9 - Vertebral Column (Bones)

Vertebral Column Overview

• Textbook Readings:

  • Wiley: 7.9

  • Open Stax: 7.3

  • Libretexts: 6.4

Structure of the Vertebral Column

• Composed of 33 vertebrae

• Divided into 5 regions:

  • Cervical (C1-C7): 7 vertebrae

  • Thoracic (T1-T12): 12 vertebrae

  • Lumbar (L1-L5): 5 vertebrae

  • Sacral (S1-S5): 5 fused vertebrae

  • Coccygeal (Co1-Co4): 3–5 fused vertebrae

Curvatures of the Spine

• The spine is not perfectly straight; it has 4 distinct curves:

  • Cervical Lordosis: inward curve of the cervical spine.

  • Thoracic Kyphosis: outward curve in the thoracic region.

  • Lumbar Lordosis: inward curve of the lumbar spine.

  • Sacral Kyphosis: outward curve of the sacral area.

Curvature Origins

• Primary Curvature (Kyphosis):

  • Thoracic (2)

  • Sacral (4)

• Secondary Curvature (Lordosis):

  • Cervical (1): develops as the head is raised.

  • Lumbar (3): develops when a child begins to walk.

Flexibility of the Vertebral Column

• Characteristics:

  • Boney cage with great flexibility.

  • Several symphyses (cartilaginous joints) contribute to flexibility.

  • Contains 23 intervertebral discs.

  • Points of articulation facilitate movement.

Differences Among Regions of the Vertebrae

• Cervical (C1-C7):

  • Smaller vertebral body compared to lumbar and thoracic.

  • Transverse processes: small extensions with foramina for blood vessels.

• Thoracic (T1-T12):

  • Larger and thicker than cervical but smaller than lumbar.

  • Long spinous processes that project inferiorly.

  • Articulates with ribs.

• Lumbar (L1-L5):

  • Largest and thickest for vertical weight support.

  • Short, stubby spinous processes that project posteriorly.

Vertebral Structures

• Vertebral Body:

  • Cylindrical mass on the anterior side:

    • Cervical: Smallest of the three regions.

    • Thoracic: Larger than cervical but smaller than lumbar.

    • Lumbar: Largest to withstand heavier loads (including head & torso).

• Vertebral Foramen:

  • Large triangular opening for spinal cord:

    • Cervical: Largest of all.

    • Thoracic: Smaller than cervical, larger than lumbar.

    • Lumbar: Smallest of the three.

• Vertebral Arch:

  • Protects spinal cord and is formed by:

    • Pedicles and laminae from each vertebra.

  • Spinous process projects posteriorly.

Articulating Facets

• Superior Articulating Facet:

  • Different orientations in each region:

    • Cervical: Posterosuperior facing, slightly concave.

    • Thoracic: Posterolateral, flattened surface.

    • Lumbar: Medial points, convex.

• Inferior Articulating Facet:

  • Different orientations in each region:

    • Cervical: Anteroinferior facing, flattened surface.

    • Thoracic: Anteriomedial point.

    • Lumbar: Lateral facing, concave surface.

Additional Structures

• Vertebral Notches:

  • Formed on pedicles, important for spinal nerve passage.

• Intervertebral Foramen:

  • Openings between adjacent vertebrae where spinal nerves exit.

• Sacrum:

  • Composed of 5 fused vertebrae, forms part of the pelvic girdle.

  • Contains sacral canal, contains remnants of the cauda equina.