Lecture 2, vertebrae and the vertebral column

Learning Objectives

  • Be able to identify the vertebrae from the cervical, thoracic, lumbar and sacral regions.

  • Know the arrangement of the vertebrae in the vertebral column

  • Know the main features of a typical vertebrae and identify the atypical vertebrae

The Vertebral Column

  • Structure: Central longitudinal bony pillar of the body.

    • Supports the skull, pectoral girdle, upper limbs, and thoracic cage.

    • Transmits body weight to lower limbs through the pelvic girdle.

    • Protects spinal cord and spinal nerves.

  • Composed of 33 vertebrae organized into 5 regions:

    • 7 cervical vertebrae

    • 12 thoracic vertebrae

    • 5 lumbar vertebrae

    • 5 fused sacral vertebrae

    • 4 coccygeal vertebrae (lower 3 commonly fused).

  • Total length in adults: 72-75 cm, with 1/4 of length being fibrocartilaginous intervertebral discs (IV discs).

Vertebral Column Curvatures

  • Adult vertebral column has 4 regional curves in the sagittal plane:

    • Thoracic and sacrococcygeal curves have anterior concavities.

    • Cervical and lumbar curves are concave posteriorly.

  • Curvatures align the center of gravity through the pelvis and help maintain upright posture.

Primary and Secondary Curves

  • Fetal vertebral column has one anterior continuous concavity.

  • As it develops:

    • Lumbosacral angle forms at L5-S1 (two anterior concave curves).

    • Cervical curvature forms as the child raises their head.

    • Lumbar curve develops as the child sits and stands.

  • Primary curves (thoracic and sacrococcygeal) are retained from prenatal development.

  • Secondary curves (cervical and lumbar) form postnatally.

  • In older age, IV disc atrophy leads to loss of height and a return to anterior concavity.

Vertebral Column Functionality

  • Curvatures provide extra flexibility and shock-absorbing resilience.

  • Flexibility is regulated by IV discs, zygapophysial joints, and longitudinal ligaments.

Typical Vertebra Structure

  • Vertebral Body: Anterior part providing strength and supporting body weight. Increases in size downward.

  • Vertebral (Neural) Arch: Formed by pedicles and laminae, creating a vertebral foramen for the spinal cord.

Processes in Typical Vertebra

  • Vertebra has seven processes:

    • 1 Spinous Process

    • 2 Transverse Processes: Articulate with ribs in the thoracic region, helping in muscle and ligament attachment.

    • 4 Articular Processes:

      • Two superior

      • Two inferior, forming zygapophysial facet joints that influence movement and alignment between vertebrae.

Intervertebral Foramina

  • Pedicles have notches enabling formation of intervertebral foramen that transmit spinal nerves and blood vessels.

Functional Components of Vertebrae

  • Support body weight.

  • Protect spinal cord.

  • Aid in movement.

  • Restrict excessive movement.

Cervical Vertebrae Characteristics

  • Seven cervical vertebrae: Small size, broad/square body with concave superior and convex inferior surface.

  • Transverse foramen for vertebral artery, veins, sympathetic plexuses (C7 only vein).

  • Unique atlas (C1) and axis (C2) vertebrae.

Atypical Cervical Vertebrae

  • C1 (Atlas): Ring-like with lateral masses, no spinous process. Articulates with the skull.

    • Lacks a vertebral body and forms a joint with the dens of C2.

  • C2 (Axis): Contains a dens projecting superiorly, allowing head rotation.

  • C7 (Vertebra Prominens): Long non-bifid spinous process, large transverse process.

Thoracic Vertebrae Specifics

  • Medium-sized heart-shaped vertebral body, articulation with ribs via costal facets.

  • Small circular vertebral foramen and long inferiorly inclined spinous process.

  • Facets allow for limited movement but facilitate rib cage function.

Lumbar Vertebrae Characteristics

  • Large kidney-shaped bodies with large triangular foramen.

  • Short, flat quadrangular spinous processes.

  • Long slender transverse processes with curved facets.

Sacral Anatomy

  • Sacrum consists of five fused vertebrae, triangular shape, stability for the pelvis.

  • Articulates with lumbar vertebrae above and coccyx below.

Coccyx Structure

  • Formed by four fused vertebrae, articulates with the sacrum.