Atlas (anatomy)

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C1 lateral

First cervical vertebra of the spine

Atlas

Position of the atlas (shown in red)
Latin	Atlas
Articulations	Axis, Occipital bone
System	Skeletal system

The atlas (C1) is the first cervical vertebra of the spine. It is named after the Atlas of Greek mythology, who supported the globe on his shoulders. The atlas is unique among the vertebrae in that it has no vertebral body or spinous process. It is a ring-like structure that supports the skull and facilitates its movement.

Structure

The atlas consists of an anterior and a posterior arch, along with two lateral masses. The anterior arch is shorter and contains the anterior tubercle. The posterior arch is longer and contains the posterior tubercle. The lateral masses are the thickest part of the atlas and contain the superior and inferior articular facets.

Anterior Arch

The anterior arch forms about one-fifth of the ring of the atlas. It has a convex anterior surface and a concave posterior surface. The anterior tubercle serves as an attachment point for the longus colli muscle.

Posterior Arch

The posterior arch forms about two-fifths of the ring of the atlas. It has a groove for the vertebral artery and the first cervical spinal nerve. The posterior tubercle serves as an attachment point for the rectus capitis posterior minor muscle.

Lateral Masses

The lateral masses are the thickest and strongest part of the atlas. The superior articular facets are concave and articulate with the occipital condyles of the occipital bone, forming the atlanto-occipital joint. The inferior articular facets are flat and articulate with the axis, forming the atlanto-axial joint.

Function

The atlas supports the skull and allows for a range of head movements. It works in conjunction with the axis to facilitate the rotation of the head. The atlanto-occipital joint allows for nodding movements, while the atlanto-axial joint allows for rotational movements.

Clinical Significance

Injuries to the atlas can result in significant neurological damage due to its proximity to the spinal cord and brainstem. Conditions such as atlantoaxial instability and Jefferson fracture are associated with the atlas.

Related Pages

• Axis (anatomy)
• Cervical vertebrae
• Atlanto-occipital joint
• Atlanto-axial joint
• Vertebral column
• Occipital bone