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.

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