Median atlanto-axial joint

Median atlanto-axial joint: Anatomy & FunctionAnatomy, function, innervation, and blood supply of the median atlanto-axial joint
~ 3 min

The vertebral column is connected to the skull by three joints: the atlanto-occipital, the median atlanto-axial and the lateral atlanto-axial joint.

Let’s learn about the structure of the median atlanto-axial joint (articulatio atlantoaxialis mediana).

Median atlanto-axial joint (art. atlantoaxialis mediana)
Median atlanto-axial joint (art. atlantoaxialis mediana)

The first one is formed between the anterior articular surface of the dens of the axis (facies articularis anterior dentis) and the facet for the dens of the atlas (fovea dentis)

Anterior articular surface of the dens of the axis (facies articularis anterior dentis)
Anterior articular surface of the dens of the axis (facies articularis anterior dentis)
Facet for the dens of the atlas (fovea dentis)
Facet for the dens of the atlas (fovea dentis)

The second joint is formed between the posterior articular surface of the dens of the axis (facies articularis posterior dentis) and the transverse ligament of the atlas (ligamentum transversum atlantis).

Posterior articular surface of the dens of the axis (facies articularis posterior dentis)
Posterior articular surface of the dens of the axis (facies articularis posterior dentis)
Transverse ligament of the atlas (lig. transversum atlantis)
Transverse ligament of the atlas (lig. transversum atlantis)

The articular capsule (capsula articularis) is attached along the edge of the facet for the dens and partially covers the dens of the axis.

Articular capsule (capsula articularis)
Articular capsule (capsula articularis)

According to the classification, this joint is cylindrical, uniaxial, simple and combined (with lateral atlanto-axial joints).

The following range of motions is possible in the joint:

  • Around the vertical axis: rotation of the head to the right and left

    The ligamentous apparatus includes several ligaments:

  • Cruciate ligament of the atlas (ligamentum cruciforme atlantis). It consists of three bundles:

    Cruciate ligament of the atlas (lig. cruciforme atlantis)
    Cruciate ligament of the atlas (lig. cruciforme atlantis)
    • The superior longitudinal fasciculus (fasciculus longitudinalis superior)

      Superior longitudinal fasciculus (fasciculus longitudinalis superior)
      Superior longitudinal fasciculus (fasciculus longitudinalis superior)
    • The inferior longitudinal fasciculus (fasciculus longitudinalis inferior)

      Inferior longitudinal fasciculus (fasciculus longitudinalis inferior)
      Inferior longitudinal fasciculus (fasciculus longitudinalis inferior)
    • The transverse ligament of the atlas (ligamentum transversum atlantis)

      Transverse ligament of the atlas (lig. transversum atlantis)
      Transverse ligament of the atlas (lig. transversum atlantis)
  • The joint is also strengthened by the alar ligaments (ligamenta alaria), which restrict excessive rotation of the head to the right and left. Each such ligament arises from the lateral surface of the dens and passes externally, obliquely and upward, where it inserts into the internal surface of the corresponding condyle of the occipital bone.

    Alar ligaments (ligg. alaria)
    Alar ligaments (ligg. alaria)
  • Another ligament is the apical ligament of the dens (ligamentum apicis dentis), it is unpaired, thin, and stretched between the edge of the foramen magnum and the apex of the dens.

    Apical ligament of the dens (lig. apicis dentis)
    Apical ligament of the dens (lig. apicis dentis)
  • And the last ligament that strengthens the joint is the tectorial membrane (membrana tectoria).

    Tectorial membrane (membrana tectoria)
    Tectorial membrane (membrana tectoria)

    The following vessels and nerves take part in the blood supply and innervation of the joint.

  • Arteries: branches of the deep cervical, occipital and vertebral arteries

  • Nerves: anterior branch of the second spinal nerve

Dictionary

Median atlanto-axial joint

Median atlanto-axial joint
articulatio atlantoaxialis mediana
Anterior articular surface of the dens
facies articularis anterior dentis
Facet for the dens
fovea dentis
Posterior articular surface of the dens
facies articularis posterior dentis
Transverse ligament of the atlas
ligamentum transversum atlantis
Articular capsule
capsula articularis
Cruciate ligament of the atlas
ligamentum cruciforme atlantis
Superior longitudinal fasciculus
fasciculus longitudinalis superior
Inferior longitudinal fasciculus
fasciculus longitudinalis inferior
Alar ligaments
ligamenta alaria
Apical ligament of the dens
ligamentum apicis dentis
Tectorial membrane
membrana tectoria
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