Which of the following is NOT considered an atypical vertebra?

The distinction between typical and atypical vertebrae is based on the specific structural features they possess. Typically, cervical vertebrae C3 through C6 are considered typical vertebrae as they share common characteristics, including the presence of a vertebral body, a spinous process, and transverse foramina.

C1 and C2, known as the atlas and axis, respectively, are classified as atypical vertebrae due to their unique structures that accommodate the specific functions of supporting the skull and facilitating head movement. The atlas lacks a vertebral body and has an arrangement that allows it to articulate with the occipital condyles of the skull, while the axis has a prominent odontoid process (dens) that allows for rotation.

Since C3 does not possess these atypical features and fits the common structure characteristic of typical cervical vertebrae, it is classified as a typical vertebra. This clarification helps to identify C3 as the correct answer to the question regarding which vertebra is NOT considered atypical.