Craniovertebral joints
Terms
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- What attaches to the anterior tubercle of the atlas?
- The upper part of the anterior longitudinal ligament and the uppermost attachment of the longus colli muscle.
- What's on the posterior tubercle of the atlas?
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A groove for the vertebral artery.
The vertebral artery passes through the transverse foramen, bends medially, lies in the groove then ascends through foramen magnum. - Which vertebra has the longest/most lateral transverse processes and why?
- The atlas, gives increased mechanical advantage to the muscles that attach there.
- Which vertebra is the strongest?
- The axis.
- Dens
- Part of the axis, articulates with the anterior arch of the atlas, and has a facet posteriorly for the transverse ligament which runs from side to side, just behind the dens.
- What forms the Atlanto-Occipial joint?
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Articular facets (kidney shaped) on the transverse processes of the atlas for reception of the occipital condyle.
Ellipsoid synovial joint. Longer transverse diameter than anterior-posterior.
Movement around two axes:
The first is around transverse axis (flexion and extension), like nodding your head yes; movement is between the occipital condyle and superior articular facets of the atlas.
The second is around the anterior-posterior axis (lateral flexion) tilting head to the side, also occurs at the AO joints. - What forms the medial Atlanto-Axial joint?
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Articulation of the dens with the anterior arch of the atlas.
Gliding synovial joints. Glide as the head turns. - What forms the lateral Atlanto-Axial joints?
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Articulation of superior articular facets of axis which articulate with the inferior articular processes of the atlas.
Pivot joint. Synovial cavities anterior and posterior to the dens, allow rotation/pivoting. When the head turns the atlas and skull turn together, the dens is stationary. - External craniocervical ligaments
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AO joint has a loose fibrous capsule lined with a synovial membrane.
Between the 2 joints anteriorly there is an [anterior] AO membrane, which stretches from the anterior arch of the atlas to the anterior margin of the foramen magnum.
The lateral AA joint also has a rather loose capsule, opened up on slide; you can see the gliding surfaces of the AA joints.
Between the lateral AA joints, you can see the upper continuation of the anterior longitudinal ligament which attaches to the anterior tubercle of the atlas.
The AO membrane is continuous with the capsules of the AO joints on either side.
Posteriorly, there is a posterior AO membrane, which stretches from the posterior arch of the atlas to the posterior margin of the foramen magnum (seen in sub-occipital triangle lab). This is pierced by the vertebral artery and sub-occipital nerve. - What membrane do the vertebral artery and sub-occipital nerve pierce?
- The posterior AO membrane, which stretches from the posterior arch of the atlas to the posterior margin of the foramen magnum.
- Internal craniocervical ligaments
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Tectorial membrane
Cruciate ligament
On a slightly deeper plane a pair of alar ligaments - Tectorial membrane
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Runs from the axis to the base of the occipital bone. Anterior to the dura mater surrounding the cervical spinal cord. A continuation of the PLL.
Cruciate ligament is deep to tectorial membrane. - Cruciate ligament
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Deep to tectorial membrane.
Related to medial AA joint.
Consists of traverse ligament, superior and inferior longitudinal bands.
The transverse ligament holds the dens against the anterior arch.
Superior to Alar ligaments - Alar ligaments
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Deep to cruciate ligament
Run superolaterally from the lateral margin of the dens to the medial margin of the occipital condyle.
Strong, big ligaments that function to limit how far the head turns. "Check ligaments".