220
UNIT 2
Covering, Support, and Movement of the Body
7
Check Your Understanding
13.
What are the five major regions of the vertebral column?
14.
In which two of these regions is the vertebral column
concave posteriorly?
15.
Besides the spinal curvatures, which skeletal elements help to
make the vertebral column flexible?
For answers, see Appendix H.
General Structure of Vertebrae
Discuss the structure of a typical vertebra and describe
regional features of cervical, thoracic, and lumbar
vertebrae.
All vertebrae have a common structural pattern
(Figure 7.19)
.
Each vertebra consists of a
body
, or
centrum
, anteriorly and a
vertebral arch
posteriorly. Te disc-shaped body is the weight-
bearing region. ±ogether, the body and vertebral arch enclose
an opening called the
vertebral foramen
. Successive vertebral
foramina of the articulated vertebrae form the long
vertebral
canal
, through which the spinal cord passes.
Te vertebral arch is a composite structure formed by two pedi-
cles and two laminae. Te
pedicles
(ped
9
ĭ-kelz; “little feet”), short
bony pillars projecting posteriorly from the vertebral body, form
the sides of the arch. Te
laminae
(lam
9
ĭ-ne), flattened plates that
fuse in the median plane, complete the arch posteriorly. Te pedi-
cles have notches on their superior and inferior borders, providing
lateral openings between adjacent vertebrae called
intervertebral
foramina
(see Figure 7.16). Te spinal nerves issuing from the
spinal cord pass through these foramina.
Seven processes project from the vertebral arch. Te
spinous
process
is a median posterior projection arising at the junction
of the two laminae. A
transverse process
extends laterally from
each side of the vertebral arch. Te spinous and transverse pro-
cesses are attachment sites for muscles that move the vertebral col-
umn and for ligaments that stabilize it. Te paired
superior
and
inferior articular processes
protrude superiorly and inferiorly,
Vertebral spinous process
(posterior aspect of vertebra)
Spinal nerve root
Anulus fibrosus
of disc
Herniated portion
of disc
Nucleus
pulposus
of disc
Spinal cord
(c) Superior view of a herniated intervertebral disc
Nucleus
pulposus of
intact disc
(d) MRI of lumbar region of vertebral column in
sagittal section showing herniated disc
Herniated
nucleus
pulposus
Transverse
process
Figure 7.18
(continued)
Ligaments and fibrocartilage discs uniting the vertebrae.
Posterior
Anterior
• Lamina
Super
ior
articular
f
acet
and
pr
ocess
Tr
ans
ve
rs
e
pr
ocess
• Pedicle
Spinous
pr
ocess
Vertebral
arch
Vert
ebral
foramen
Body
(centrum)
Figure 7.19
Typical vertebral structures.
Superior view of a tho-
racic vertebra. Only bone features are illustrated in this and subsequent
bone figures in this chapter. Articular cartilage is not depicted.
disc
(commonly called a
slipped disc
) usually involves rupture
of the anulus fibrosus followed by protrusion of the spongy nu-
cleus pulposus through the anulus (Figure 7.18c, d). If the pro-
trusion presses on the spinal cord or on spinal nerves exiting
from the cord, numbness or excruciating pain may result.
Herniated discs are generally treated with moderate exercise,
massage, heat therapy, and painkillers. If this fails, the protruding
disc may have to be removed surgically and a bone gra² done to
fuse the adjoining vertebrae. For those preferring to avoid general
anesthesia, part of the disc can be vaporized with a laser in an out-
patient procedure called percutaneous laser disc decompression
that takes only 30 to 40 minutes. If necessary, tears in the anulus
can be sealed by electrothermal means at the same time. Te pa-
tient leaves with only an adhesive bandage to mark the spot.
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