Atypical cervical vertebrae. Atlas (C1)

Atypical cervical vertebrae. Atlas (C1): Anatomy & FunctionKey facts about the anatomy of the first cervical vertabra – the Atlas (C1)
~ 3 min

The first cervical vertebra (C1) is called the atlas. It is an atypical cervical vertebra that has its own distinctive characteristics.

The atlas (C1)
The atlas (C1)

It does not have a body; during the embryonic period, it transformed into a dens of the 2nd cervical vertebra (C2). The role of the body is performed by two lateral masses (massa lateralis).

Lateral mass (massa lateralis)
Lateral mass (massa lateralis)

At the top and bottom of each lateral mass there are superior and inferior articular surfaces (facies articulares superior et inferior). It is necessary to clarify that there are no articular processes, only surfaces.

The superior articular surfaces are connected to the occipital bone and the inferior articular surfaces are connected to the 2nd cervical vertebra (C2).

Superior articular surface (facies articularis superior)
Superior articular surface (facies articularis superior)
Inferior articular surface (facies articularis inferior)
Inferior articular surface (facies articularis inferior)

The two lateral masses are connected by the anterior arch of the atlas (arcus anterior atlantis);

Anterior arch (arcus anterior atlantis)
Anterior arch (arcus anterior atlantis)

and the posterior arch of the atlas (arcus posterior atlantis)

Posterior arch (arcus posterior atlantis)
Posterior arch (arcus posterior atlantis)

There is an anterior tubercle (tuberculum anterius) on the anterior arch, and a posterior tubercle (tuberculum posterius) on the posterior arch. The latter plays the role of the spinous process, which the atlas does not have.

Anterior tubercle (tuberculum anterius)
Anterior tubercle (tuberculum anterius)
Posterior tubercle (tuberculum posterius)
Posterior tubercle (tuberculum posterius)

On the internal surface of the anterior arch, the facet for the dens (fovea dentis) can be seen, which serves to connect to the dens of the 2nd cervical vertebra.

Facet for the dens (fovea dentis)
Facet for the dens (fovea dentis)

On the posterior arch, there is a small impression — the groove for the vertebral artery (sulcus arteriae vertebralis).

Groove for the vertebral artery (sulcus arteriae vertebralis)
Groove for the vertebral artery (sulcus arteriae vertebralis)

To the side of each lateral mass extends a transverse process (processus transversus).

Transverse process (processus transversus)
Transverse process (processus transversus)

As with the other cervical vertebrae, there is a foramen transversarium, through which passes the vertebral artery, involved in the blood supply to the brain.

Foramen transversarium
Foramen transversarium

In the very center of the atlas is the vertebral foramen (foramen vertebrale).

Vertebral foramen (foramen vertebrale)
Vertebral foramen (foramen vertebrale)
Dictionary

Atlas (C1)

atlas
atlas
massa lateralis
lateral mass
facies articularis superior
superior articular surface
facies articularis inferior
inferior articular surface
arcus anterior atlantis
anterior arch
arcus posterior atlantis
posterior arch
tuberculum anterius
anterior tubercle
tuberculum posterius
posterior tubercle
fovea dentis
facet for dens
sulcus arteriae vertebralis
groove for vertebral artery
processus transversus
transverse process
foramen transversarium
foramen transversarium
foramen vertebrale
vertebral foramen
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