The inferior articular surfaces have the same direction as those of the other cervical vertebrae. The superior vertebral notches are very shallow, and lie behind the articular processes. The inferior vertebral notches lie in front of the articular processes, as in the other cervical vertebrae. The spinous process is large, very strong, deeply channelled on its under surface, and presents a bifurcated extremity. Variation
Contact sports are contraindicated for individuals with anomalous dens, as any violent impact may result in a catastrophic injury. This is because a malformed odontoid process may lead to instability between the atlas and axis (the C1 and C2 cervical vertebrae). Development
The axis is ossified from five primary and two secondary centres. The body and vertebral arch are ossified in the same manner as the corresponding parts in the other vertebrae, viz., one centre for the body, and two for the vertebral arch. The centres for the arch appear about the seventh or eighth week of fetal life, while the centres for the body appear in about the fourth or fifth month. The dens, or odontoid process, consist originally of a continuation upward of the cartilaginous mass, in which the lower part of the body is formed.
This type can be stable or unstable and may require surgery. [1]

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See also
References
This article incorporates text in the public domain from page 99 of the 20th edition of Grays Anatomy (1918)

External links
Netter, Frank. Atlas of Human Anatomy Archived 2017-11-20 at the Wayback Machine, "High Cervical Spine: C1-C2"