Cervical Vertebrae Anatomy

• The cervical column curves forward.
• Atlas transverse processes (C1 vertebra) are the widest.
• Axis spinous processes (C2 vertebra) are the most massive, located deep within extensor muscles.
• The change in curvature between cervical and thoracic spine makes C7 spinous process project backwards.
• C7 is referred to as vertebra prominens due to its prominent spinous process, but T1 may sometimes be more prominent.
• Atlas and axis facilitate head nodding and rotation.
• C3-6 are "typical" cervical vertebrae, due to the atlas, axis, and C7 having their own unique features.

Typical Cervical Vertebrae (C3-C6)

• The kidney-shaped vertebral body is broad, and approximately the same size or smaller than the vertebral foramen.
• Posterolateral lips (uncus) project upwards on each side.
• The lower margin is beveled laterally, and projects slightly downwards in the midline.
• The flat upper and lower surfaces attach to the intervertebral disc.
• The upturned lips and beveled margins are located on the neural arch.
• Basivertebral foramina are more widely spaced than in thoracic and lumbar vertebrae.
• Basivertebral veins emerge from the foramina.
• The anterior surface of the body is concave, and the anterior longitudinal ligament is firmly attached to it.
• Longus colli overlies the anterior longitudinal ligament.
• The pedicle attaches below the upturned lip on the body.
• Intervertebral foramen of the neck are bounded anteriorly by vertebral bodies, the uncovertebral joint, and the disc.
• The lateral projection of the transverse process is attached to the pedicle and body and is perforated by a foramen.
• The posterior bar of bone that projects from the pedicle behind the foramen is a true transverse element, ending in the posterior tubercle, which is part of the costal element.
• The bar of bone in front of the foramen ends in the upturned anterior tubercle.
• Anterior tubercles increase from C3 to C6.
• C6's large anterior tubercle is called the carotid tubercle (of Chassaignac), and the common carotid artery can be compressed against it.
• The anterior and posterior tubercles are joined by the intertubercular lamella.
• The anterior bar and tubercle, the lamella, and the posterior tubercle form the costal element, a vestigial rib fused to the vertebra.
• The vertebral artery runs through the foramen of the transverse process.
• The posterior root ganglion of the corresponding nerve lies behind it on the lamella.
• Longus capitis, scalenus anterior, and longus colli tendons attach to the anterior tubercle.
• Scalenus medius originates from the posterior tubercle.
• Levator scapulae originates from posterior tubercles down to C4, and scalenus posterior from C5 and 6 (and 7).
• The relatively large vertebral foramen is triangular.
• The borders are grooved for ligamenta flava.
• Superior and inferior articular processes are at the junction of the pedicle and lamina.
• Articular facets are formed from the superior and infereior processes.
• The upper facets face obliquely up and back in the same plane.
• The lower facets face down and forward.
• The capsule and synovial membrane attach to the articular margins.
• The spinous process is usually bifid, with concavities for semispinalis cervicis.

Atypical Cervical Vertebrae

• The seventh cervical vertebra (vertebra prominens) has a prominent spine and may be a misnomer.
• The long spine is not bifid, ending in a rounded tubercle.
• The transverse process foramen does not transmit the vertebral artery.
• The anterior tubercle:
  • Is very smal
  • Attaches to scalenus pleuralis and the suprapleural membrane

Atlas (C1)

• Kidney-shaped facets for the occipital bone are deeply concave front to back, and gently concave side to side.
• The tubercle in the "hilum" of each "kidney" attaches to the transverse ligament, which stabilizes the dens of the axis.
• The short anterior arch has a concave facet for the synovial joint with the dens.
• The anterior tubercle attaches to the anterior longitudinal ligament and longus colli.
• The upper border of the anterior arch carries the anterior atlanto-occipital membrane between the atlanto-occipital joint capsules.
• The longer posterior arch is a semicircle.
• The vertebral artery and C1 nerve groove the upper surface at the root of the arch.
• The upper border of the posterior arch attaches to the posterior atlanto-occipital membrane
• The lower border receives the ligamentum flavum from the axis.
• Dimples at the posterior convexity of the arch give rise to the rectus capitis posterior minor muscles.
• The lateral mass carries weight-bearing articular facets.
• Lower facets are circular and flat, or gently concave, and articulate with the axis' superior articular facets.
• The transverse process is perforated by the foramen.
• Anterior and lateral bone to the vertebrarterial foramen is costal in origin.
• The internal jugular vein and accessory nerve lie on the transverse process.
• The transverse process attaches to obliquus capitis superior and inferior, splenius cervicis, and levator scapulae.
• Rectus capitis anterior and lateralis attach to the lateral mass.

Axis (C2)

• C2 acts as a pivot for head and atlas rotation.
• The dens (odontoid process) projects upwards from the body between the lateral mass's weight-bearing areas.
• Weight is communicated from the lateral masses through the body to the C3 vertebra.
• C2 and C3 articulations resemble those of the rest of the vertebral column.
• Anteriorly, the dens has a cylindrical facet for a synovial joint with the anterior arch of the atlas.
• The posterior surface of the dens usually has a bursa to lubricate movements of the transverse ligament during head rotation.
• The apex of the dens carries:
  • The apical ligament (a remnant of the notochord).
  • Alar ligaments, one on either side.
• The body shows the bevel along the lateral margin of its lower surface.
• The anterior longitudinal ligament attaches to the front of the body, overlaid by longus colli and the prevertebral fascia.
• The posterior surface of the body attaches to:
  • The longitudinal band of the cruciform ligament.
  • The tectorial membrane (sweeps up from the attachment of the posterior longitudinal ligament).
• The upper surface of the body features a pair of large facets that slope down from the dens.
• Each surface has a synovial joint with the facet on the lateral mass of the atlas.
• The costal element slopes steeply down and ends in a transverse process.
• The transverse process represents the posterior tubercle of a typical cervical vertebra.
• The foramen in the transverse process is directed upwards and outwards, giving a lateral bend to the vertebral artery.
• Scalenus medius, splenius cervicis, and levator scapulae attach to the transverse process.
• An inferior articular process extends down from the junction of the pedicle and lamina; its articular facet faces downwards and forwards.
• The thick laminae project posteriorly into a spinous process.
• The upper border of the ridged spinous process, is grooved and has a wide bifurcation.
• Semispinalis cervicis muscles insert into the spinous process' concavity, and rectus capitis posterior major and the inferior oblique diverge from the outer surface on either side.
• Upper and lower borders of the thick laminae attach to the ligamenta flava.
• The posterior surface of the laminae attaches to multifidus and longissimus.

Development of Vertebrae

• Vertebrae develop from the sclerotome parts of the mesodermal somites.
• Sclerotomes surround the notochord and neural tube in a mesoderm sheath.
• Cartilaginous rings appear in the mesodermal sheath.
• Each ring ossifies in three centers to form the centrum and the two halves of the neural arch of a vertebra.
• Each ring is formed by the fusion of adjacent halves (caudal and cranial) of the original somites.
• Vertebrae lie in the intersegmental planes, not in segments of the body wall.
• Vertebrae ossify in hyaline cartilage.
  • The centrum has a double center that rapidly fuses; failure of one half results in hemivertebra.
  • The centrum and neural arch halves ossify by the eighth week of fetal life.
• Cartilage between the two halves of the neural arch ossifies after birth and is completely bony by age 2.
• Neurocentral junctions ossify and there should be bony union by age 7.
• Vertical cylindrical surface of the body is covered with compact bone and The flat upper and lower surfaces, covered with hyaline cartilage.
• Epiphyses for the body appear as bony rings soon after puberty.
• Fusion of the epiphyseal ring and body occurs in the early twenties. -Vertebra of an adolescent shows irregular radial grooves at the circumference of upper and lower surfaces when separated from its annular epiphysis.
• Soon after puberty, secondary centers appear at:
  • The tip of the spinous process.
  • The tips of the transverse processes.
  • The mamillary processes of T12 and the lumbar vertebrae.
• These fuse in the early twenties.
• Costal elements of cervical and lumbar vertebrae do not have a separate bony center; they ossify via direct extension from the neural arch.
• An occasional center in the costal element of C7 or LI vertebra may lead to the formation of a cervical or lumbar rib.
• The sacrum's weight-bearing costal elements have bony centers.
  • These appear at 6 months of fetal life and fuse with the neural arches at about 5 years.
  • They fuse with each other and with the sacral bodies in the early twenties.
• The atlas ossifies in the seventh week with a center in each lateral mass.
  • These extend around the posterior arch and unite at the fourth year.
  • A center in the anterior arch appears at the first year; it joins the bone of the lateral mass.
  • These epiphyses fuse at 7 years. This epiphyseal junction may permanently divide the articular surface.
• The axis has primary centers for:
  • The lower part of the body (fifth month).
  • Each half of the arch and lateral part (seventh week).
  • Each half-side of the dens extending to the upper part of the body (fifth month, fusing to form a single center 2 months later), uniting with the rest of the body at 3 years.
• A secondary center for the tip of the dens appears at about 3 years and fuses at 12.
• An epiphyseal ring for the lower part of the body appears at puberty and fuses at about 25 years.