the Vertebral Column

The Vertebral Column

  • The vertebral column extends from the skull to the pelvis.

Curvatures of the Vertebral Column

  • The vertebral column possesses four curvatures:

    • Anterior Concave Curvatures:

      • Thoracic Curve

      • Sacrococcygeal Curve

    • Posterior Concave Curvatures:

      • Cervical Curve

      • Lumbar Curve

  • Purpose of these curvatures:

    • Enhance resilience and strength in an upright posture compared to a straight column.

  • Disorders Associated with Curvatures:

    • Scoliosis: Involves an abnormal lateral curvature of the vertebral column, resembling an 'S' or 'C' shape.

Naming of Vertebrae

  • Vertebrae are named according to their anatomical regions:

    • Cervical (7 vertebrae: C1-C7)

    • Thoracic (12 vertebrae: T1-T12)

    • Lumbar (5 vertebrae: L1-L5)

    • Sacrum (1 fused segment)

    • Coccyx (tail region, typically 4-5 fused vertebrae)

  • When vertebrae join, they form a canal called the vertebral foramen, through which the spinal cord passes.

Structure of Individual Vertebrae

  • Variations in Structure:

    • Each vertebra varies slightly in structure depending on its region:

      • Cervical Vertebrae:

        • Spinous processes are long with bifid tips (except for C1).

        • Vertebral bodies are small.

        • Vertebral foramina are large, with transverse processes that feature transverse foramina for the passage of vertebral arteries and veins.

        • First two cervical vertebrae are specialized:

          • Atlas (C1): Lacks a body; has lateral masses for articulation with the occipital condyles for head flexion and extension.

          • Axis (C2): Contains the dens (odontoid process) for head rotation.

      • Thoracic Vertebrae:

        • Long, thin spinous processes that do not split, pointing inferiorly.

        • Medium-sized vertebral bodies with costal facets for rib articulation.

        • Twelve thoracic vertebrae total; rib articulation is present on all except T11 and T12.

      • Lumbar Vertebrae:

        • Shorter and broader spinous process, projecting posteriorly.

        • The largest vertebrae, supporting the weight of the upper body.

        • Transverse processes are shorter and lack costal facets.

        • Vertebral foramina are the smallest and triangular in shape.

      • Sacrum:

        • Comprised of five fused bones; articulates with L5 at its base.

        • Crucial for pelvic stability and provides attachment sites for ligaments and tendons.

      • Coccyx:

        • Made up of typically four or five fused vertebrae; begins to fuse by around age 25.

Spinal Curves

  • Primary Curves: Develop before birth.

  • Secondary Curves: Develop after birth.

    • Cervical Curve: Develops as the infant learns to hold its head up.

    • Thoracic Curve: A primary curve that accommodates thoracic organs.

    • Lumbar Curve: A secondary curve formed to balance the trunk over the lower limbs as walking begins.

    • Sacral Curve: A primary curve that accommodates abdominopelvic organs.

Abnormal Spinal Curvatures

  • Scoliosis: Abnormal lateral curvature of the vertebral column.

  • Kyphosis: Excessive outward curvature of the upper vertebral column, causing a hunched back.

  • Lordosis: Excessive inward curvature of the lumbar vertebrae, leading to protrusion of the abdomen and buttocks.

Bone Markings of the Vertebrae (Table 3)

  • Key bone markings:

    • Body (Centrum): Rounded central portion; connects with intervertebral discs.

    • Vertebral Arch: Comprised of:

      • Pedicles: Lateral sides of the arch.

      • Laminae: Part of the arch between the transverse process and the spinous process.

    • Vertebral Foramen: Large opening for the spinal cord.

    • Transverse Processes: Paired projections facilitating attachment and movement.

    • Spinous Process: Posterior projection; midline of vertebrae.

    • Superior and Inferior Articular Processes: Join adjacent vertebrae together.

Characteristics of Vertebrae by Type (Table 4)

  • Cervical Vertebrae (C3-C7):

    • Great range of movements permitted: flexion, extension, lateral flexion, rotation.

    • Body: Small but wide with costal facets.

    • Spinous Process: Short and bifid, projecting posteriorly.

    • Vertebral Foramen: Triangular.

    • Transverse Process: Contains foramina.

  • Thoracic Vertebrae:

    • Movements: Rotation; limited lateral flexion due to ribs.

    • Body: Heart-shaped with costal facets.

    • Spinous Process: Long and sharp, projects downward.

    • Vertebral Foramen: Circular.

    • Transverse Process: Facets for ribs.

  • Lumbar Vertebrae:

    • Movements: Flexion and extension permitted; no rotation.

    • Body: Large and kidney-shaped.

    • Spinous Process: Short and blunt, projecting posteriorly.

    • Vertebral Foramen: Triangular.

    • Transverse Process: Thin and tapered.

The Thoracic Cage

  • The thoracic cage consists of:

    • Posterior: Thoracic vertebrae

    • Laterally: Ribs

    • Anteriorly: Costal cartilages and sternum.

  • Function: Protects thoracic cavity organs (heart, lungs, thymus) and provides attachment sites for muscles involved in:

    • Breathing

    • Positioning of the vertebral column and pectoral girdle.

Ribs

  • Twelve pairs of ribs connect to the thoracic vertebrae:

    • True Ribs (Ribs 1-7): Connect directly to the sternum via costal cartilage.

    • False Ribs (Ribs 8-12):

      • Ribs 8-10 connect via costal cartilage of superior rib.

      • Ribs 11-12 are called "floating ribs" as they do not attach to the sternum.

Sternum

  • A flat bone on the anterior midline, comprising three parts:

    • Manubrium: Articulates with clavicles and rib 1.

    • Body: Attaches ribs 2-7.

    • Xiphoid Process: Attaches to the diaphragm and rectus abdominis muscle.