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Atlas general qualities
- ring shaped vertebra that lack a body and a spine
- 2 eliptical lateral masses that conect by a short anterior arch and a longer curved posterior arch.
What occupies the position of the body of the atlas
the dens of the axis to form a pivot around which the atlas and skull turn
Posterior tubercle of atlas
Represents the spine of the atlas on the posterior arch
Anterior tuberlce of atlas.
midline on the anterior arch
Superior facet of the atlas face?
elongated and concave and face medially
Articulation of the superior facets of the atlas?
the convex occipital condyles to form the pair AO joint
Shape of the inferior facet of the atlas
circular, flat or slightly concave, and face medially and slightly backwards
articulations of the inferior facet of the atlas
superior facets of the axis to form the paired lateral atlanto-axial joints
What grooves the posterior arch on its uppwer surface behind each lateral mass?
vertebral artery and veins
transverse processes of the atlas
project laterally and anteriorly and are palpable between the mastoid process and angle of the mandible.
What runs through the foramen of the transverse process of the atlas
Dens of the axis
projects upward from the body of the axis. Articulates in front with the anterior arch of the atlas and behind with the transverse ligament of the atlas to form the median atlanto-axial joint
Superior articular facets of the axis attributes
large oval, convex anteroposteriorly and flat or concave transversely.
superior articular facets of the axis articulation
with the inferior facets of the atlas at the lateral AA joints
Spine of Axis attributes
- large, bifid
- transverse processes short and blunt
- the pedicles and laminae thick
What connects the OA joint?
anterior and posterior atlanto-occipital membranes that extend from the anterior and posterior arches of the atlas to the anterior and posterior margins of the foramen magnum
what encloses the AO joint?
an articular capsule that is thin and loose.
What kind of joint is the AO joint?
biaxial ellipsoid joint
What are the movements of the AO joint?
- FLEX and EXT as in "YES"
- Slight side bending to one or the other side
What are the synovial joint betwen the atlas and axis
2 lateral plane joint and a median pivot joint
How many synovial joints are at the AA? where?
2 lateral plan joints and a median pivot joint
Lateral AA joint
Plane joint between the opposed articular facets of the Atlas and axis.
Capsule of the lateral AA joint
- thin and loose
- strengthened posteromedially by an accessory AA ligament
median atlato-axial joint type of joint and formation?
uniaxial pivot between the dens of the axis and the ring formed by the anterior arch of the atlas and its transverse ligament.
What are the 2 articulations and synovial cavities of the AA joint?
one between the front of the dens and atnerior arch, the other between the back of the dens and transverse ligament.
What is the transverse ligament of the atlas
a thick strong band that extends between the tubercles on the medial surfaces of the lateral masses of the atlas. Passes behind the dens and holds it in contact with the anterior arch.
Where does the superior band of the transverse ligament of the atlas pass?
from the middle of the ligamnet then upward to the atnerior edy of the foramen magnum
Where does the inferior band of the transverse ligament of the atlas pass?
from the middle of the ligament then downward to the back of the nody of the axis
What makes up the cruciform ligament of the atlas?
the transverse ligament of the atlas with the superior and inferior bands.
Movement of the AA joints
- primarily rotation of the skull and atlas on the axis as in "NO"
- contribute to FLEX and EXT of the neck.
What limits the AA rotation?
the Alar ligaments
What serves as a pivot around the atlas and skull turn?
the dens of the axis
Membrana tectoria attributes
- broad, thick band that cobvers the dens and its ligaments within the vertebral canal.
- betwn the axis and the occipital bone
What is the upward extension of the posterior longitudinal ligament?
the membrana tectoria
Where does the membrana tectoria run?
from the body of the axis it expands as it passes upward and is attached to the basilar part of the occipital bone in front of the foramen magnum
Alar ligament attributes
- between the axis and the occipital bone
- strong rounded cords that arise on either side of the apex of the dens
Where does the alar ligament run?
pass upward and laterally to the medial side of each occipital condyle.
What do the alar ligaments limit
extent of rotation at the AA joints
apical ligament of the dens
a slender band that extends from the apex of the dens to the anterior margin of the foramen magnum
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