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Spine sections
| The spine
is made up of 24 vertebrae and 110 joints. There are 3 sections:
7 cervical, 12 dorsal or thoracic and 5 lumbar vertebrae. The
cervical, or neck section, is the most mobile. In the thoracic
section each vertebrae has a rib attached to it on each side.
Below the lumbar section is the diamond-shaped sacrum which
locks like a keystone into the pelvis. The joints between the
sides of the sacrum and the rest of the pelvis are called the
sacroiliac joints. This is usually the starting-point of the
condition where the low back pain and AS begin. |
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Spine
The spinal, or vertebral, column is one of the primary support
structures for the human skeleton. Made up of separate, pseudoseparate,
and fused vertebrae, the spine features a great deal of articulation,
allowing support and movement of the skull, flexion of the neck
and back, anchor sites for the ribs (which enclose the abdominal
cavity), and support and protection for the spinal cord. The spine
is composed of seven cervical vertebrae, forming the neck, twelve
thoracic vertebrae, which form the upper back, and five lumbar
vertebrae, which form the lower back. Also part of the spinal
column is the sacrum, a bone made of five fused vertebrae which
anchors the spine to the pelvic girdle, and the coccyx, or tailbone,
a semi-flexible series of four or less vertebrae which help to
protect the lower alimentary tract. Between each vertebra is an
intervertebral disk made of cartilage, which acts as a shock absorber,
to cushion the vertebral column from trauma. The spine is held
together by a series of ligaments, including the intertransverse
ligaments which run the length of the spine, attached to the transverse
processes of each vertebra. The spinal cord, which serves as the
primary nerve pathway to and from the brain, proceeds down a canal
in the centre of the spinal column. - return
to top
Cervical Vertebrae
The cervical vertebrae are the first (upper) seven in the vertebral
column. The first cervical vertebra is the atlas, so called because
it directly bears the weight of the skull. The second cervical
vertebra is called the axis, because it admits the rotation of
the skull by allowing the atlas to pivot upon it. The other five
cervical vertebrae have no names, but are called by their number
(i.e., third cervical vertebra). Each of the cervical vertebra
features a body (anterior, or frontal, portion) and an arch (posterior,
or rear, portion). The body of each vertebra in the column bears
the weight of the vertebrae above it (and the skull), while the
arch serves to create a canal-like area along the spine to house
and protect the spinal cord. Every cervical vertebra has a foramen
(opening) in each of its transverse processes (lateral protrusions).
The arch of the vertebra features a small knob or prominence,
called an anterior tubercle. The anterior tubercles on the sixth
cervical vertebra are particularly large and are known as the
carotid tubercles. - return to top
Atlas
The atlas is the first of the seven cervical vertebrae, and is
called such because it bears the direct weight of the skull, just
as the mythical Greek hero Atlas bore the world on his shoulders.
The atlas vertebra meets with the occipital condyles which flank
the foramen magnum in the basilar part of the occipital bone of
the skull. This junction forms the atlanto-occipital joint, and
is responsible for the primary articulation between the spine
and the skull. It is the only vertebra in the spine which has
no vertebral body. The atlas vertebra, in turn rests upon the
axis vertebra, which is the second of the cervical vertebra in
the spine, with the articulation between these two vertebra occurring
at lateral articular surfaces and an unique juncture between a
concave facet (on the atlas) and an upward-protruding structure
on the axis called a dens. - return
to top
Axis
The axis is the second of the seven cervical vertebrae, and is
called such because it allows axial (rotational) movement of the
skull. The axis lies directly beneath the atlas vertebra, their
junction occurring at lateral articular surfaces and an unique
juncture between a concave facet (on the atlas) and an upward-protruding
dens (on the axis). This articulation is regulated by the alar
ligament, which attaches to both atlas and axis. - return
to top
Thoracic Vertebrae
The thoracic vertebrae are the middle twelve in the vertebral
column. Most of the thoracic vertebrae feature costal (relating
to the ribs) facets on the body and transverse processes of the
vertebra, no foramina in the transverse processes (as the cervical
vertebra have), a spinous process which points back and down,
and a round vertebral foramen. The body of each thoracic vertebra
in the spinal column bears the weight of the vertebrae above it
(and the skull), while the arch serves to create a canal-like
area along the spine to house and protect the spinal cord. - return
to top
Transverse Processes
Most vertebrae exhibit pronounced lateral protrusions (or processes),
one on each side of the vertebra. These transverse processes serve
as the attachment sites for ligaments (intertransverse ligaments)
and muscles, which control the bending and twisting of the vertebral
column. The base of each transverse process in most vertebrae
is just off of the main body of the vertebra, located instead
at the pedicle. The pedicle is part of the ring-like structure
of a vertebra, which also includes the body and lamina of a vertebra,
forming the vertebral foramen which protects the spinal cord.
- return to top
Intervertebral Disks
Cartilage disks are located between the vertebrae, and serve
to cushion the spinal column from shock. Each disk features an
inner, pulpy centre, called the nucleus pulposus, and a fibrous
outer ring, called the annulus fibrosus, which is visible in a
lateral view of the spine. These intervertebral disks are easily
torn or dislocated when the vertebra column is subjected to inordinate
stresses, such as those encountered in lifting a heavy load improperly,
or twisting the back sharply, as occurs in many sporting injuries.
Such a "slipped" disk is only one of many causes of
back pain. Others include arthritis, spinal meningitis, and inflammation
of a tendon or muscle. Such back problems can cause extreme pain,
which may be increased by changes in the weather or poor diet,
making lifting, walking, and sitting an excruciating ordeal. Since
so many muscles place stress on the spine when they operate, simple
activities such as going to the bathroom, coughing, laughing,
and even breathing may be intolerable with such a condition. More
recently, however, medical advances have enabled a number of these
ailments to be alleviated and chiropractic, arthroscopic surgery,
and other forms of physical therapy make much suffering unnecessary.
- return to top
Lumbar Vertebrae
The lumbar vertebrae are the five vertebrae which are below the
thoracic vertebrae and above the fused vertebrae of the sacrum.
The lumbar vertebrae feature no facets on the body or transverse
processes (as the thoracic vertebrae have) and the bodies of the
lumbar vertebrae are much larger than those of the cervical or
thoracic vertebrae. The vertebral foramen is usually triangular,
while the spinous process points backward and is rectangular or
hatchet-shaped. The transverse processes of the lumbar vertebrae
(which also represent their rib elements) lack the foramina which
characterise the cervical vertebrae. The large body of each lumbar
vertebra bears the weight of the vertebrae above it (and the skull),
while the arch serves to create a canal-like area along the spine
to house and protect the spinal cord. - return
to top
Coccyx
The coccyx (or "tailbone") is composed of from three
to five rudimentary vertebrae. Often, the first of these coccygeal
vertebrae is separate, while the remainder are fused together.
The articulation between the coccygeal vertebrae and the sacrum
allow some flexibility in the coccyx, which is particularly beneficial
in taking the stresses of sitting and falling. The coccyx is extremely
susceptible to shock fracture, as might be induced from a fall.
Furthermore, since a number of nerve pathways pass near this area,
damage to the coccyx threatens damage to the nerves of the lower
body. The juncture of the first coccygeal vertebra with the sacrum
occurs at the lower facet of the sacrum. - return
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