Anatomy of the Face - Flipbook - Page 46
Cervical Spine
The cervical spine is home to the spinal cord that sends messages from the brain to control all aspects of the
body, while also remarkably strong and flexible, allowing the neck to move in all directions. The neck is
connected to the upper back through a series of seven vertebral segments.
The cervical spine also allows passage of important vasculature to reach the brain and provides attachment sites
for muscles that move the head, neck, and shoulder girdle. At each level, the cervical vertebrae protect the
spinal cord and work with muscles, tendons, ligaments, and joints to provide a combination of support, structure,
and flexibility to the neck.
The bony component of the cervical spine is made up of seven vertebrae. The lower five are more similar to each
other than the upper two (atlas – C1, axis – C2).
Atypical cervical vertebrae: The atlas (C1), axis (C2) and C7
Atlas (C1)
Unlike other vertebrae, the atlas does not have a spinous process or a body. When seen from above, the atlas is
really a ring shape. The atlas connects to the occipital bone above to support the base of the skull and form the
atlanto-occipital joint. More of the head’s forward/backward range of motion occurs at this joint compared to
any other spinal joint.
Axis (C2)
The axis is more similar to the rest of the cervical spine vertebrae than the atlas but it does have an incredibly
unique feature; the dens, or odontoid process. Often characterized as tooth-like or peg-like, this process is larger
and longer than most other anatomical processes and extends from the body of C2. The dens and the spinal
cord are encircled by the atlas. The dens makes an articulation with the posterior surface of the anterior arch of
the atlas (the median atlantoaxial joint) and is held in place by the transverse ligament. The dens, and its
articulation with the atlas, acts as a pivot around which rotation of the head can occur, forming the atlantoaxial
joint. More rotational range of motion occurs at this joint compared to any other, with some estimates being that
nearly half of the head’s rotation occurs at this joint.
C7
C7 Is atypical for three reasons. The first is that the spinous process of C7 is the longest and can be easily
palpated when the head is flexed forward as it is quite prominent in this position.
Intervertebral discs
Although not technically a bony component, the intervertebral discs lie in between all cervical vertebrae with the
exception of C1 and C2. These discs can be quite significant clinically as they make up the inferior half of the
anterior border of the intervertebral and vertebral foramina. They are also considered to create symphysis joints
(a type of cartilaginous joint) with the vertebrae superior and inferior to each disc, providing the spinal column
with rigidity. The discs allow movement between vertebrae, but also function as shock absorbers, providing a
cushion between the vertebrae during weight-bearing activities. The outer component of the disc is known as the
annulus fibrosus. It is made of fibrocartilage, and functions to contain the inner segment of the disc: the nucleus
pulposus.
Cervical vertebrae C3 through C6 are known as typical vertebrae because they share the same basic
characteristics with most of the vertebrae throughout the rest of the spine. Typical vertebrae have:
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Vertebral body. This thick bone is cylindrical-shaped and located at the front of the vertebra. The vertebral
body carries most of the load for a vertebra. At most levels of the spine, an intervertebral disc sits between 2
vertebral bodies to provide cushioning and help absorb the shock of everyday movements.
•
Vertebral arch. This bony arch wraps around the spinal cord toward the back of the spine and consists of 2
pedicles and 2 laminae. The pedicles connect with the vertebral body in the front, and the laminae transition
into the spinous process (a bony hump) in the back of the vertebra.
•
Facet joints. Each vertebra has a pair of facet joints, also known as zygapophysial joints. These joints, located
between the pedicle and lamina on each side of the vertebral arch, are lined with smooth cartilage to
enable limited movement between 2 vertebrae. Spinal degeneration or injury to the facet joints are among
the most common causes of chronic neck pain.
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