The alar ligaments connect the sides of the dens

Dens

Dens may refer to:* Den *Dens , also known as odontoid process or odontoid peg*Tooth...

 (on the axis, or the second cervical vertebra

Cervical vertebrae

In vertebrates, cervical vertebrae are those vertebrae immediately inferior to the skull.Thoracic vertebrae in all mammalian species are defined as those vertebrae that also carry a pair of ribs, and lie caudal to the cervical vertebrae. Further caudally follow the lumbar vertebrae, which also...

) to tubercles on the medial

Medial

- Medial magmas :In abstract algebra, a medial magma is a set with a binary operation which satisfies the identity \cdot = \cdot , or more simply, xy\cdot uv = xu\cdot yv...

 side of the occipital condyle

Occipital condyle

The occipital condyles are undersurface facets of the occipital bone in vertebrates, which function in articulation with the superior facets of the atlas vertebra....

.

They are short, tough, fibrous cords that attach the skull

Human skull

The human skull is a bony structure, skeleton, that is in the human head and which supports the structures of the face and forms a cavity for the brain.In humans, the adult skull is normally made up of 22 bones...

 to C2 vertebra (via the dens) and function to check side-to-side movements of the head

Head

In anatomy, the head of an animal is the rostral part that usually comprises the brain, eyes, ears, nose and mouth . Some very simple animals may not have a head, but many bilaterally symmetric forms do....

when it is turned.

The alar ligament is also known as the "check ligament of the odontoid."