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• Vertebrae

  • There are approximately 33 vertebrae
  • Subdivided into five groups based on morphology and location
• Cervical vertebrae


  • 7 vertebrae between the thorax and skull
  • Characterized by small size
  • Presence of a foramen in each transverse process
• Thoracic vertebrae


  • 12 vertebrae
  • Characterized by articulated ribs
  • Ribs are separate bones and articulate via synovial joints with the vertebral bodies and transverse processes
• Lumbar vertebrae


  • 5 vertebrae
  • Form the skeletal support for the posterior abdominal wall
  • Characterized by large size
• Sacral vertebrae


  • 5 vertebrae fused into one single bone called the sacrum
  • Articulates on each side with a pelvic bone
  • Component of the pelvic wall
• Coccygeal vertebrae


  • Variable number, usually 4
  • Fuse into a single small triangular bone called the coccyx
• Vertebrae formation


  1. Formed intersegmentally from cells called sclerotomes

  2. Originate from adjacent somites

  3. Each vertebra derived from cranial parts of two somites below and caudal parts of two somites above

  4. Spinal nerves develop segmentally and pass between the forming vertebrae
• Typical vertebra


  Consists of a vertebral body and a posterior vertebral arch
• Vertebral body


  • Weight-bearing part of the vertebra
  • Linked to adjacent vertebral bodies by intervertebral discs and ligaments
  • Size increases inferiorly as the amount of weight supported increases
• Vertebral arch


  • Forms the lateral and posterior parts of the vertebral foramen
• Vertebral foramina


  Together form the vertebral canal, which contains and protects the spinal cord
• Vertebral arch


  Consists of pedicles and laminae
• Pedicles


  • Bony pillars that attach the vertebral arch to the vertebral body
• Laminae


  • Flat sheets of bone that extend from each pedicle to meet in the midline and form the roof of the vertebral arch
• Spinous process


  • Projects posteriorly and inferiorly from the junction of the two laminae and is a site for muscle and ligament attachment
• Transverse process


  • Extends posterolaterally from the junction of the pedicle and lamina on each side and is a site for muscle and ligament attachment, and for articulation with ribs in the thoracic region
• Articular processes


  • Superior and inferior processes that articulate with the inferior and superior articular processes, respectively, of adjacent vertebrae
• Vertebral notches


  Superior and inferior notches in each pedicle that participate in forming intervertebral foramina
• Cervical vertebrae


  • Seven in number
  • Characterized by their small size and the presence of a foramen in each transverse process
• Typical cervical vertebra


  • Vertebral body is short in height and square shaped when viewed from above, with a concave superior surface and a convex inferior surface
  • Each transverse process is trough shaped and perforated by a round foramen transversarium
  • The spinous process is short and bifid
  • The vertebral foramen is triangular
• The first and second cervical vertebrae—the atlas and axis—are specialized to accommodate movement of the head
• Atlas


  Vertebra CI that articulates with the head
• Atlas


  • Lacks a vertebral body
  • Vertebral body of CI fuses onto the body of CII during development to become the dens of CII
  • No intervertebral disc between CI and CII
  • Ring shaped and composed of two lateral masses interconnected by an anterior arch and a posterior arch
• Atlanto-occipital joint


  Allows the head to nod up and down on the vertebral column
• Dens


  Tooth-like projection that extends superiorly from the vertebral body of the axis
• Dens


  • Has an oval facet on the anterior surface for articulation with the anterior arch of the atlas
  • Has two superolateral circular impressions that serve as attachment sites for alar ligaments
• Alar ligaments

  Connect the dens to the medial surfaces of the occipital condyles and check excessive rotation of the head and atlas relative to the axis
• Axis


  Vertebra CII characterized by the large tooth-like dens
• Transverse processes of the atlas

  • Large and protrude further laterally than those of the other cervical vertebrae
  • Act as levers for muscle action, particularly for muscles that move the head at the atlanto-axial joints
• Thoracic vertebrae


  • 12 in number
  • Articulate with ribs
• Typical thoracic vertebra


  • Has two partial facets (superior and inferior costal facets) on each side of the vertebral body for articulation with the head of its own rib and the head of the rib below
  • Superior costal facet is much larger than the inferior costal facet
  • Each transverse process also has a facet (transverse costal facet) for articulation with the tubercle of its own rib
  • Vertebral body is somewhat heart shaped when viewed from above
  • Vertebral foramen is circular
• Lumbar vertebrae


  • 5 in number
  • Larger in size
  • Lack facets for articulation with ribs
  • Transverse processes are generally thin and long, except for vertebra LV which are massive and somewhat cone shaped for the attachment of iliolumbar ligaments to connect the transverse processes to the pelvic bones
• Typical lumbar vertebra


  • Vertebral body is cylindrical
  • Vertebral foramen is triangular in shape and larger than in the thoracic vertebrae
• Sacrum

  • Single bone representing 5 fused sacral vertebrae
  • Triangular in shape with the apex pointed inferiorly
  • Curved with a concave anterior surface and a convex posterior surface
  • Articulates above with vertebra LV and below with the coccyx
  • Has two large L-shaped facets, one on each lateral surface, for articulation with the pelvic bones
  • Posterior surface has 4 pairs of posterior sacral foramina
  • Anterior surface has 4 pairs of anterior sacral foramina for the passage of the posterior and anterior rami of S1 to S4 spinal nerves
  • Posterior wall of the vertebral canal may be incomplete near the inferior end
• Coccyx


  • Small triangular bone
  • Articulates with the inferior end of the sacrum
  • Represents 3 to 4 fused coccygeal vertebrae
  • Lacks vertebral arches and therefore a vertebral canal
• Intervertebral foramina


  Formed on each side between adjacent parts of vertebrae and associated intervertebral discs, allowing structures such as spinal nerves and blood vessels to pass in and out of the vertebral canal
• Formation of intervertebral foramen

  1. Inferior vertebral notch on the pedicle of the vertebra above

  2. Superior vertebral notch on the pedicle of the vertebra below
• Intervertebral foramen


  • Bordered posteriorly by the zygapophysial joint between the articular processes of the two vertebrae
  • Bordered anteriorly by the intervertebral disc and adjacent vertebral bodies
• Intervertebral foramen


  A confined space surrounded by bone and ligament, and by joints
• Pathology in any of the structures surrounding the intervertebral foramen


  Can affect structures within the foramen