Atlas: anatomy, location and function

Also called

C1

What it is

The first cervical vertebra (C1), a ring-shaped bone that supports the skull.

Location

Lies at the top of the vertebral column, between the occipital bone above and the axis (C2) below.

Function

Carries the skull and allows the head to nod ('yes' movement) at the atlanto-occipital joints.

Body system

Skeletal · single, midline structure

FMA ID

FMA12519 (Foundational Model of Anatomy)

Key facts

• It has no vertebral body and no spinous process; it consists of anterior and posterior arches joined by two lateral masses.
• The superior articular facets articulate with the occipital condyles; the inferior facets articulate with the axis.
• The dens of the axis fits against the inner surface of its anterior arch, held by the transverse ligament of the atlas.

Clinical relevance

A burst fracture of the ring of the atlas is called a Jefferson fracture.

The nearest named structures in the 3D model, measured from the centre of each part:

• Central canal of spinal cord · nervous
• Anterior spinal artery · cardiovascular
• Medulla oblongata · nervous
• Axis · skeletal
• Rectus capitis anterior · muscular
• Vertebral artery · cardiovascular
• Intervertebral disk of axis · skeletal
• Obliquus capitis inferior · muscular
• Rectus capitis posterior major · muscular
• Rectus capitis lateralis · muscular