Question

which of the following is only found on the axis vertebra?

superior articular facet
spinous process
dens (odontoid process)
vertebral arch
transverse foramen

Explanation:

Identify the target structure and question

The question asks which of the listed anatomical features is only found on the axis vertebra (the second cervical vertebra, C2).

Analyze the anatomical options

• Superior articular facet: Found on almost all vertebrae to articulate with the vertebra above.
• Spinous process: A standard feature present on most vertebrae (C2 through L5) for muscle and ligament attachment.
• Dens (odontoid process): A prominent, tooth-like projection pointing superiorly from the body of the axis (C2). It is a unique, defining feature of C2 that projects into the vertebral foramen of the atlas (C1) to act as a pivot for head rotation.
• Vertebral arch: A basic structural component of almost all vertebrae, forming the posterior portion of the vertebral foramen.
• Transverse foramen: A characteristic feature of all cervical vertebrae (C1–C7) that accommodates the vertebral artery, not unique to C2.

Determine the unique feature of C2

The dens (odontoid process) is the only feature listed that is exclusively found on the axis (C2) vertebra.

Answer:

• Superior articular facet
• Spinous process
• Dens (odontoid process) (Correct answer)
• Vertebral arch
• Transverse foramen