Human Anatomy

Alar ligaments

The ligaments that connect the sides of the odontoid process of the second cervical vertebra to the sides of the foramen magnum.

Alar ligaments are important connective tissues that help stabilize the cervical spine. They extend from the apex of the odontoid process, which is the bony projection of the second cervical vertebra (C2 or axis), to the inner sides of the foramen magnum, the large opening at the base of the skull. These ligaments are crucial in maintaining the alignment of the head and neck.

Terminologia Anatomica

ligamenta alaria

System

Musculoskeletal system

Function

The primary function of the alar ligaments is to provide stability and restrict excessive movement between the skull and the cervical spine, particularly during rotational movements. When the head turns, the alar ligaments play a significant role in preventing over-rotation and ensuring the integrity of the craniovertebral junction. This protective function is vital for avoiding injuries that could affect the spinal cord or surrounding neural structures. Furthermore, their unique positioning contributes to the coordination of head and neck movements, allowing for a wide range of motions while maintaining balance and posture.

Location

Alar ligaments are located at the uppermost part of the vertebral column, where the spine meets the skull. Specifically, they are situated within the craniovertebral junction, extending from the top of the odontoid process of the axis (C2) upward to their attachment at the foramen magnum of the occipital bone. This location is critical, as it lies in proximity to the brain stem, which is responsible for many vital functions, thus highlighting the importance of these ligaments in protecting both the brain and the spinal cord.

Did You Know?

Alar ligaments are often referred to as 'check ligaments' because they check the movement of the head and neck, limiting excessive rotation.
Injuries or abnormalities of the alar ligaments can lead to conditions such as atlantoaxial instability, which can have serious neurological consequences.
Alar ligaments are strong yet relatively thin, highlighting their efficiency in stabilizing the cervical spine without adding excessive bulk.