Atlas Vertebra: Introduction
The atlas bone is the first of seven cervical vertebrae (vertebra cervicalis I or C1), and it supports the weight of the skull. The name for the bone was derived from a deity of Greek mythology called Atlas, who supported the heavens.
On the superior surface of the atlas bone are a pair of concave facets. The facets articulate with rounded condyles on the underside of the skull’s occipital bone. This junction allows the head to nod up and down.
Directly below the atlas bone is the axis bone (C2). Pivot and gliding joints linking the two bones allow the head to move side-to-side.
a. Lateral mass (Massa lateralis atlantis) is the thickest part of the bone. This sturdy region supports the weight of the skull.
b. Superior articular facet (Facies articularis superior) is an oval-shaped, concave structure on the superior aspect of the lateral mass. It articulates with an occipital condyle on the underside of the skull.
c. Inferior articular facet (Facies articularis inferior) is a flattened surface on the inferior lateral mass tht articulates with the superior articular facet on the axis vertebra (C2).
d. Transverse process (Processus transversus) is a prominent lateral projection from the lateral mass. It serves as an attacment site for muscles that move the head and neck.
e. Transverse foramen (Foramen transversarium) is a hole in the transverse process that serves as a passageway for the vertebral artery and vein.
f. Vertebral (spinal) foramen (Foramen vertebrale) is a large opening in the center of the bone through which the spinal cord passes.
g. Anterior arch (Arcus anterior atlantis) is a band of bone that extends medially from the transverse processes and encloses the anterior portion of the vertebral foramen.
h. Anterior tubercle (Tuberculum anterius atlantis) is a slight elevation at the apex of the anterior arch. It is an attachment point for the longus coli muscles.
i. Posterior arch (Arcus posterior atlantis) is a narrow band of bone that extends from the transverse processes and encloses the posterior portion of the vertebral foramen.
j. Posterior tubercle (Tuberculum posterius atlantis) is a slight elevation at the apex of the posterior arch. It is an attachment site for the nuchal ligament and rectus capitis posteriores minor, a suboccipital muscle.