Overview
This lecture covers the craniovertebral joints—where the skull meets the first two cervical vertebrae (C1 and C2)—and the supporting ligaments and muscles, emphasizing anatomical features and clinical relevance.
Bony Structures of the Craniovertebral Junction
- The occipital bone forms the base of the skull, featuring the foramen magnum and occipital condyles.
- Occipital condyles articulate with the atlas (C1) to form the atlanto-occipital joint.
- Atlas (C1) lacks a vertebral body and has anterior and posterior arches connected by lateral masses.
- Axis (C2) has the odontoid process (dens), which projects superiorly to articulate with C1.
- The median atlanto-axial joint is between the dens and anterior arch of C1; lateral atlanto-axial joints are on either side.
Joint Function and Movements
- Atlanto-occipital joint allows mainly flexion and extension of the head, with limited lateral flexion.
- Atlanto-axial joints (mainly median) permit rotation of the head.
- C1 and C2's orientation enables a wide range of motion but increases vulnerability.
Ligaments and Membranes
- The transverse ligament of the atlas wraps behind the dens, stabilizing the median atlanto-axial joint.
- Alar ligaments extend from the dens to the occipital bone, limiting excessive rotation.
- The apical ligament connects the tip of the dens to the occipital bone's basion.
- Anterior and posterior atlanto-occipital and atlanto-axial membranes are continuous with the anterior and posterior longitudinal ligaments and ligamentum flavum.
- Ligaments become membranes near the skull to allow increased movement while maintaining stability.
Key Muscles Supporting the Joints
- Prevertebral muscles: Longus capitis (attaches C3–C6 to occipital bone) and longus colli (from cervical vertebral bodies up to the anterior arch of C1).
- Rectus capitis anterior and rectus capitis lateralis connect C1 to the occipital bone.
- Suboccipital muscles:
- Rectus capitis posterior major (C2 spinous to occipital bone) and minor (C1 posterior arch to occipital bone).
- Obliquus capitis superior (C1 transverse process to occipital bone) and inferior (C2 spinous to C1 transverse process).
Key Terms & Definitions
- Occipital condyle — Skull surface articulating with C1.
- Atlas (C1) — First cervical vertebra, supports the skull.
- Axis (C2) — Second cervical vertebra with the dens.
- Dens/Odontoid process — Superior projection from C2.
- Atlanto-occipital joint — Joint between occipital condyle and atlas.
- Atlanto-axial joint — Joints between atlas and axis.
- Transverse ligament of the atlas — Holds dens in place.
- Alar ligaments — Limit head rotation.
- Rectus capitis/obliquus capitis — Suboccipital muscles stabilizing and moving the skull.
Action Items / Next Steps
- Review anatomical models and CT images to identify key structures.
- Study the detailed courses and attachments of craniovertebral ligaments and muscles.
- Prepare for exam questions labeling and identifying craniovertebral anatomy.