The vertebral column
The spinal, or vertebral, column is made up of thirty-three vertebrae, of
which twenty-four are discrete vertebrae and nine are fused in the sacrum
and coccyx.
In the embryo the spine is curved into a gentle C shape but, with the
extension of the head and lower limbs that occurs when the child first holds
up its head, then sits and then stands, secondary forward curvatures
appear in the cervical and lumbar region, which produce the sinusoidal
curves of the fully developed spinal column.
The basic vertebral pattern is that of a body and of a neural arch
surrounding the vertebral canal.
The neural arch is made up of a pedicle on either side, each supporting a
lamina which meets its opposite posteriorly in the midline. The pedicle
bears a notch above and below which, with its neighbour, forms theintervertebral foramen. The arch bears a posterior spine, lateral transverse
processes and upper and lower articular facets.
The intervertebral foramina transmit the segmental spinal nerves as
follows: C1–7 pass over the superior aspect of their corresponding cervical
vertebrae, C8 passes through the foramen between C7 and T1, and all sub-
sequent nerves pass between the vertebra of their own number and the one
below.
Now to consider the individual vertebrae in turn.
The cervical vertebrae (7)
These are readily identified by the foramen transversarium perforating the
transverse processes. This foramen transmits the vertebral artery, the vein,
and sympathetic nerve fibres. The spines are small and bifid (except C1
and C7 which are single) and the articular facets are relatively horizontal.
The atlas (C1) has no body. Its upper surface bears a superior
articular facet on a thick lateral mass on each side which articulates with the
occipital condyles of the skull.
Just posteriorly to this facet, the upper aspect of the posterior arch of the
atlas is grooved by the vertebral artery as it passes medially and upwards to
enter the foramen magnum.
The axis (C2) bears the dens (odontoid process) on the superior
aspect of its body, representing the detached centrum of C1.
Nodding and lateral flexion movements occur at the atlanto-occipital
joint, whereas rotation of the skull occurs at the atlanto-axial joint around
the dens, which acts as a pivot.
C7 is the vertebra prominens, so called because of its relatively long and
easily felt non-bifid spine; it is the first clearly palpable spine on running
one’s fingers downwards along the vertebral crests, although the spine of
T1 immediately below it is, in fact, the most prominent one.
The vertebral artery enters its vertebral course nearly always at the
foramen transversarium of C6; it is not surprising, therefore, that the
foramen of C7, which transmits only the vein, is small or even sometimes
absent.
The thoracic vertebrae (12)
These vertebrae are characterized by demifacets on the sides of their bodies
for articulation with the heads of the ribs and by facets on their transverse
processes (apart from those of the lower two or three vertebrae) for the rib
tubercles. The spines are long and downward sloping and the articular
facets are also relatively vertical. The lowest couple are rather ‘lumbar’ in
appearance, have a single facet on the side of the body and no facet on the
transverse process.
The bodies of T5 and T8 are worth noting; they come into relationship
with the descending aorta and are a little flattened by it on their left flank. If
the descending aorta becomes aneurysmally dilated, these four vertebral
bodies become eroded by its pressure, although their avascular interverte-
bral discs remain intact. You can make this diagnosis confidently when
shown a specimen of four partly worn-away vertebrae with normal inter-
vening discs.
The lumbar vertebrae (5)
These are of great size with strong, square, horizontal spines and with
articular facets which lie in the sagittal plane.
L5 is distinguished by its massive transverse process which connects
with the whole lateral aspect of its pedicle and encroaches on its body; the
transverse processes of the other lumbar
vertebrae attach solely to the junc-
tion of pedicle with lamina.
The sacrum (5 fused)
The coccyx (3, 4 or 5 fused)
The spinal, or vertebral, column is made up of thirty-three vertebrae, of
which twenty-four are discrete vertebrae and nine are fused in the sacrum
and coccyx.
In the embryo the spine is curved into a gentle C shape but, with the
extension of the head and lower limbs that occurs when the child first holds
up its head, then sits and then stands, secondary forward curvatures
appear in the cervical and lumbar region, which produce the sinusoidal
curves of the fully developed spinal column.
The basic vertebral pattern is that of a body and of a neural arch
surrounding the vertebral canal.
The neural arch is made up of a pedicle on either side, each supporting a
lamina which meets its opposite posteriorly in the midline. The pedicle
bears a notch above and below which, with its neighbour, forms theintervertebral foramen. The arch bears a posterior spine, lateral transverse
processes and upper and lower articular facets.
The intervertebral foramina transmit the segmental spinal nerves as
follows: C1–7 pass over the superior aspect of their corresponding cervical
vertebrae, C8 passes through the foramen between C7 and T1, and all sub-
sequent nerves pass between the vertebra of their own number and the one
below.
Now to consider the individual vertebrae in turn.
The cervical vertebrae (7)
These are readily identified by the foramen transversarium perforating the
transverse processes. This foramen transmits the vertebral artery, the vein,
and sympathetic nerve fibres. The spines are small and bifid (except C1
and C7 which are single) and the articular facets are relatively horizontal.
The atlas (C1) has no body. Its upper surface bears a superior
articular facet on a thick lateral mass on each side which articulates with the
occipital condyles of the skull.
Just posteriorly to this facet, the upper aspect of the posterior arch of the
atlas is grooved by the vertebral artery as it passes medially and upwards to
enter the foramen magnum.
The axis (C2) bears the dens (odontoid process) on the superior
aspect of its body, representing the detached centrum of C1.
Nodding and lateral flexion movements occur at the atlanto-occipital
joint, whereas rotation of the skull occurs at the atlanto-axial joint around
the dens, which acts as a pivot.
C7 is the vertebra prominens, so called because of its relatively long and
easily felt non-bifid spine; it is the first clearly palpable spine on running
one’s fingers downwards along the vertebral crests, although the spine of
T1 immediately below it is, in fact, the most prominent one.
The vertebral artery enters its vertebral course nearly always at the
foramen transversarium of C6; it is not surprising, therefore, that the
foramen of C7, which transmits only the vein, is small or even sometimes
absent.
The thoracic vertebrae (12)
These vertebrae are characterized by demifacets on the sides of their bodies
for articulation with the heads of the ribs and by facets on their transverse
processes (apart from those of the lower two or three vertebrae) for the rib
tubercles. The spines are long and downward sloping and the articular
facets are also relatively vertical. The lowest couple are rather ‘lumbar’ in
appearance, have a single facet on the side of the body and no facet on the
transverse process.
The bodies of T5 and T8 are worth noting; they come into relationship
with the descending aorta and are a little flattened by it on their left flank. If
the descending aorta becomes aneurysmally dilated, these four vertebral
bodies become eroded by its pressure, although their avascular interverte-
bral discs remain intact. You can make this diagnosis confidently when
shown a specimen of four partly worn-away vertebrae with normal inter-
vening discs.
The lumbar vertebrae (5)
These are of great size with strong, square, horizontal spines and with
articular facets which lie in the sagittal plane.
L5 is distinguished by its massive transverse process which connects
with the whole lateral aspect of its pedicle and encroaches on its body; the
transverse processes of the other lumbar
tion of pedicle with lamina.
The sacrum (5 fused)
The coccyx (3, 4 or 5 fused)
No comments:
Post a Comment