anatomy of craniovertebral region or C1 and C2 vertebrea

1. THE CERVICAL SPINE VIBHUTI NAUTIYAL
MPT (MUSCULOSKELETAL)

2. STRUCTURE
Consists of 7 vertebrae in total
Divided into 2 distinct parts:
a. The upper cervical spine or cranio-vertebral region
b. The lower cervical spine
Cranio-vertebral region includes the occipital condyles and C1-C2
Lower cervical spine includes the vertebrae of C3-C7

3. CRANIO-VERTEBRAL REGION
A. ATLAS:
Function of the atlas is to cradle the occiput and to transmit forces
from the occiput to the lower cervical spine.
It has no V.B or spinous process
Shaped like a ring
There are 2 large lateral masses that have a vertical alignment under
each occipital condyle that transmit forces
The lateral masses are connected by an anterior and posterior arch
that form the ring structure and also creates large transverse process
for muscle attachments

4. The lateral masses include 4 articulating facets:
a. 2 superior facets
b. 2 inferior facets
Atlas also possesses a facet on the internal surface of the anterior arch for
articulation with the dens of axis
Superior zygapophseal facets:
a. Large
b. Kidney shaped
c. Deeply concave to accommodate the large convex articular surfaces of
the occipital condyles

7. Inferior zygapophyseal facets:
a. Slightly convex
b. Directed inferiorly
c. Articulates with the superior zygapophyseal facets of the axis

9. B. AXIS:
Primary function of the axis are:
a. Transmit the combined load of the head and the atlas
b. Provide motion into axial rotation of the head and atlas
Anterior portion of the body extends inferiorly and a vertical
projection called the dens arises from the superior surface of the
body
Dens has an anterior facet for articulation with the anterior arch of
the atlas and a posterior groove for articulation with the transverse
ligament

10. The arch of the axis has inferior and superior zygapophyseal facets
for articulation
The spinous process is large and elongated with a bifid tip
Superior facets face upward and laterally
Inferior facets face anteriorly

13. ARTICULATIONS
A. ATLANTO-OCCIPITAL JOINT:
Composed of the right and left deep concave superior facets of the
atlas that articulates with the right and left convex occipital condyles
True synovial joint
Lie nearly in the horizontal plane

15. B. ATLANTO-AXIAL JOINT:
3 synovial joint
1 median (pivot joint) and 2 lateral joint
Median joint consists of odontoid process of C2 that articulated with
a facet on the internal surface of the atlas (C1)
2 lateral joints are composed of right and left superior facets of the
axis that articulates with the right and left slightly convex inferior
facet on the atlas

17. CRANIO VERTEBRAL LIGAMENTS
A. 4 of the ligaments are continuation of the longitudinal tract
system:
a. Posterior atlanto-occipital and atlanto-axial membranes:
Continuation of the ligamentum flavum
Less elastic
Therefore permit greater ROM, especially into rotation
b. Anterior atlanto-occipital and atlanto-axial membranes:
Continuation of ALL

19. c. Tectorial membrane:
Continuation of the PLL in the upper 2 segments
Broad and strong
Originates from the posterior V.B of axis
Covers the dens and its cruciate ligament
Inserts at the anterior rim of the foramen magnum

21. d. Ligamentum nuchae:
Thick
Extends from the spinous process of C7 to the external occipital
protuberance
Evolution of the supraspinous ligament
Resist the flexion moment of head

23. B. Transverse ligament:
Stretches across the ring of the atlas
Divides the ring into a large posterior section for the spinal cord
Has a thin layer of articular cartilage on its anterior surface for
articulation with the dens
Longitudinal fibres extend superiorly to attach to the occipital bone
Inferior fibres descend to the posterior portion of the axis
Transverse portion holds the dens in close approximation against the
anterior ring of the atlas

25. Prevent anterior displacement of C1 and C2
Transverse atlantal ligament is very strong and the dens will fracture
before the ligament will tear
C. Alar ligament:
2 alar ligament
Arise from the axis or either side of the dens
Extend laterally and superiorly to attach to roughened areas on the
medial sides of the occipital condyles and to the lateral masses of the
atlas

26. Relaxed with the head in mid-position or neutral
Taut in flexion and rotation of the head and neck
Right upper and left lower portion limit left lateral flexion
Prevent distraction of C1 and C2
Weaker than the transverse atlantal ligament
Runs in a fan shaped arrangement from the apex of the dens to the
anterior margin of the foramen magnum of the skull