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Lateral Masses of C1/Atlas

The atlas a.k.a. C1 is the first vertebra of the spinal column. It connects with the occipital bone, which, is a flat bone located at the posterior part of the head. The atlas is made up of:

  • Anterior arch
  • Posterior arch
  • Paired lateral masses
  • Paired transverse processes
Composition of Atlas

Composition of Atlas

Lateral Masses


  • Its upper and lower surfaces respectively, create superior and inferior articular facets:
    • The superior articular facet is stretched out as well as concave. In order to create the atlanto-occipital joint, it is pointed upwards as well as medially to create joint with the equivalent condyle of the occipital bone.
    • The inferior articular facet is flat as well as round. In order to create the atlantoaxial joint, it is pointed inferior, medially and backwards for join creation with the equivalent facet on the axis vertebra.
  • A small irregular tubercle indicates the medial surface of the lateral mass in order to provide attachment for the transverse ligament of the atlas.
  • From the lateral masses the transverse processes project laterally. Compared to other cervical vertebrae they are stronger and larger. For the rotation of the atlas vertebra, the elongated transverse processes function as levers.
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