Anatomy of the Vertebral Column

Overview of the Vertebral Column

  • Also known as the spine, spinal column, or backbone.

  • Houses the spinal cord within the vertebral cavity.

  • Functions:

    • Distributes weight to lower limbs.

    • Supports the head.

    • Allows attachment of muscles and ligaments.

    • Facilitates movement and stability.

  • Part of the axial skeleton.

  • Composed of 33 individual bones during youth, classified as irregular bones.

Fusion of Bones

  • Nine of these bones at the terminal end of the spine fuse during adulthood.

  • Fused bones form two larger structures:

    • Sacrum

    • Coccyx

  • After fusion, the typical vertebral column consists of 26 bones.

Five Regions of the Vertebral Column

  • Anatomists categorize the vertebral column into five regions:

    1. Cervical Region

    • Comprises 7 cervical vertebrae (C1 to C7).

    • Corresponds to the neck area.

    • Mnemonic: "Seven" and "Cervical" both start with the same sound.

    1. Thoracic Region

    • Comprises 12 thoracic vertebrae (T1 to T12).

    • Articulates with the 12 pairs of ribs, forming part of the thoracic cage.

    • Mnemonic: "Twelve" and "Thoracic" both start with the letter "T."

    1. Lumbar Region

    • Comprises 5 lumbar vertebrae (L1 to L5).

    • Vertebrae are larger and denser, capable of supporting the upper body weight.

    • Mnemonic: The association of lower back pain after a 9 to 5 job implies five lumbar vertebrae.

    1. Sacral Region

    • Composed of 1 sacrum, which consists of 5 fused sacral vertebrae (S1 to S5).

    • Triangular bone that articulates with hip bones laterally and the coccyx inferiorly.

    • Forms part of the bony pelvis.

    1. Coccygeal Region

    • Comprises 1 coccyx, consisting of 3 to 5 fused coccygeal vertebrae (CO1 to CO5 or CO3 depending on fusion).

    • Also referred to as the tailbone, marking the terminal end of the vertebral column.

Intervertebral Discs

  • There are 23 intervertebral discs between the vertebrae:

    • Function: Separate, anchor, and cushion vertebrae.

  • Notable absences of intervertebral discs:

    • Between C1 (Atlas) and C2 (Axis).

    • Between sacrum and coccyx.

  • Characteristics of Intervertebral Discs:

    • Thickness increases as you move down the spine, serving as shock absorbers.

    • Composed of two main parts:

    1. Nucleus Pulposus

      • Gel-like center consisting of water, collagen, and proteoglycans.

      • Etymology: "Nucleus" signifies the core + "Pulposus" indicates pulp-like consistency.

    2. Annulus Fibrosis

      • Comprises concentric, ring-like layers of fibrocartilage surrounding the nucleus pulposus.

      • Made of type I and type II collagen.

      • Each layer's fibers are arranged at oblique angles with alternating patterns, forming a crisscross structure.

  • The discs are capped with thin cartilaginous end plates at the top and bottom.

Curvatures of the Vertebral Column

  • The vertebral column presents an S-shaped curve from the side, showing four main curvatures:

    • Primary Curvatures (Kyphotic Curves):

    • Present during fetal development.

    • Convex and curve outward towards the back of the body.

    • Include:

      • Thoracic curvature (T1 to T12).

      • Sacrococcygeal curvature (sacrum and coccyx).

    • Secondary Curvatures (Lordotic Curves):

    • Develop postpartum.

    • Concave and curve inward towards the front of the body.

    • Include:

      • Cervical curvature (C1 to C7).

      • Lumbar curvature (L1 to L5).

Future Learning Resources

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