General features of cervical vertebrae
All cervical vertebrae (vertebrae cervicales) have a number of unique characteristics that make it easy to distinguish them from vertebrae of other regions. The most important detail is the transverse foramen (foramen transversarium). It is formed as a result of the fusion of the true transverse process (processus transversus) and the rudimentary cervical rib (rudimentum costae). This foramen is clearly demarcated by bone tissue both anteriorly and posteriorly.
On the transverse process itself, you can find the sulcus of the spinal nerve (sulcus nervi spinalis), which lies between the costal rudiment and the process. The edges of the transverse process end in two projections: the anterior and posterior tubercles (tuberculum anterius et posterius). An exception is the sixth cervical vertebra (C₆). Its anterior tubercle is considerably more developed than the others and is called the carotid tubercle (tuberculum caroticum). This name is due to the fact that the common carotid artery runs in close proximity to it.
Other typical features of cervical vertebrae include:
- Small-sized bodies, on the margins of which uncinate processes (processus uncinatus) project upwards.
- Large triangular vertebral foramen.
- An almost horizontal orientation of the articular processes and their articular facets.
- Short spinous processes that are most often bifurcated at the end (bifid), although individual variations are possible.
Atlas (C₁): the first cervical vertebra
The first cervical vertebra is called the atlas (atlas). This is a completely atypical vertebra: it has neither a body (corpus) nor a spinous process (processus spinosus). Its structure consists of two lateral masses (massae laterales), which are connected to each other by anterior and posterior arches.
Important articular surfaces are located on the lateral masses:
- The superior articular surface (facies articularis superior) is oval, deep, and concave. It is required for articulation with the occipital condyles (condyli occipitales).
- The inferior articular surface (facies articularis inferior) is flatter and rounder, designed to articulate with the second cervical vertebra.
The anterior arch (arcus anterior atlantis) features on its inner side the fovea for the dens (fovea dentis), which receives the process of the underlying vertebra. Externally, this arch bears the anterior tubercle.
The posterior arch (arcus posterior atlantis) is provided with a posterior tubercle, which functionally replaces the spinous process. On the upper part of this arch, closer to the lateral masses, runs the sulcus for the vertebral artery (sulcus arteriae vertebralis). Sometimes the bone tissue grows to such an extent that the sulcus turns into a full-fledged canal (canalis arteriae vertebralis).
The transverse processes of the atlas are a direct continuation of the lateral masses and, like those of other cervical vertebrae, contain a transverse foramen for blood vessels.
Axis (C₂)
The second cervical vertebra is known as the axis (axis) or epistropheus (epistropheus). The main anatomical landmark of this vertebra is the upward-directed dens (dens axis).
The structure of the dens includes the apex (apex dentis) and two articular surfaces:
- The anterior articular surface (facies articularis anterior) forms a joint with the facet for the dens on the anterior arch of the atlas.
- The posterior articular surface (facies articularis posterior) abuts the transverse ligament of the atlas (ligamentum transversum atlantis).
Otherwise, the axis resembles typical elements of the cervical region. It has an arch that bounds the vertebral foramen (foramen vertebrale), as well as superior and inferior articular processes. Its spinous process is very massive, directed posteriorly, and bifurcated, which allows it to be used as a landmark for determining the correct position of the bone. The transverse processes also have foramina for the passage of the artery.
Vertebra prominens (C₇)
The seventh cervical vertebra (C₇) terminates the cervical region and is called the vertebra prominens (vertebra prominens). It received this name due to its long, massive, and non-bifurcated spinous process, which is easily palpated under the skin on the back of the neck. This process serves as a convenient landmark for finding the border between the cervical and thoracic regions of the vertebral column.
The shape of the body of the seventh vertebra already strongly resembles the bodies of thoracic vertebrae. Another important difference lies in the transverse foramina (foramina transversaria). In the vertebra prominens, they are noticeably smaller than in its superior neighbors. While the vertebral artery (a. vertebralis) together with veins (vv. vertebrales) passes through the foramina from C₃ to C₆, only veins pass through the foramina of C₇.
Briefly: answers to topical questions
Which ligaments are involved in fixing the dens of the axis in the median atlantoaxial joint?
The dens of the axis is fixed in the median atlantoaxial joint by a ligamentous apparatus consisting of three structures.
- The transverse ligament of the atlas (lig. transversum atlantis) runs posterior to the dens, holding it in place, and contacts its posterior articular surface.
- The alar ligaments (ligg. alaria) are thick internal ligaments.
- The apical ligament of the dens (lig. apicis dentis) is a thin apical ligament.
What structures lie in the sulcus for the vertebral artery on the posterior arch of the atlas?
The atlantoaxial part of the vertebral artery lies in the sulcus for the vertebral artery on the posterior arch of the atlas.
- The vertebral artery (arteria vertebralis) passes through the groove of the same name (sulcus arteriae vertebralis), which is located on the superior surface of the posterior arch of the atlas closer to the lateral masses.
Sometimes this sulcus can turn into a closed foramen — the canal of the vertebral artery (canalis arteriae vertebralis).
In the formation of which joints do the uncinate processes of the cervical vertebral bodies participate?
The uncinate processes of the cervical vertebral bodies participate in the formation of uncovertebral joints.
- The uncovertebral joints (joints of Luschka) are formed by the superior projections of the lateral surfaces of the C₃–C₇ vertebral bodies (uncinate processes, or processus uncinatus), which articulate with the vertebra above.
These joints are present at levels from C₂–C₃ to C₆–C₇. They provide flexion and extension, limit lateral movements, and protect against lateral and foraminal herniated discs.
To remember atypical vertebrae: C₁ (Atlas) — a ring without a body, C₂ (Axis) — has a dens for rotation, C₇ (Vertebra prominens) — has the longest non-bifurcated spinous process.
Class and exam questions
How to distinguish any cervical vertebra from a thoracic or lumbar one?
The main distinguishing feature of all cervical vertebrae is the presence of a through transverse foramen (foramen transversarium) in the transverse process.
Why is the tubercle on the sixth cervical vertebra called the carotid tubercle?
The anterior tubercle of the sixth cervical vertebra (C₆) is well developed and is called the carotid tubercle because the common carotid artery runs in close proximity to it.
Does the vertebral artery pass through the seventh cervical vertebra?
No, only vertebral veins pass through the small transverse foramina of the seventh cervical vertebra (C₇), and the artery does not enter them.
What do the superior articular surfaces of the atlas articulate with?
The oval and deep superior articular surfaces of the first cervical vertebra form a joint with the occipital condyles of the skull.
What else to study on this topic
- Formation of the transverse foramen from the rib rudiment
- Features of the articular surfaces of the lateral masses of the atlas
- Points of articulation of the dens of the axis with the atlas
- Differences in the structure of the spinous processes of typical and atypical cervical vertebrae
- Uncinate processes and their role in the structure of the vertebral body
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