Fundamentals of Anatomy and Physiology

244 Chapter 10 (^)
(^) Posterior median sulcus (^)
Anterior commissure^
(^) Posterior column Posterior horn (^)
White matter^ Lateral column^ Lateral horn^ Gray matter^
Anterior column
Anterior horn (^)
(^)
Central canal^
Posterior root Anterior median fissure (^)
ganglion (^)
Posterior or (^)
Dorsal root Pia mater (^)
Anterior or (^) Arachnoid mater
Ventral root (^)
Spinal nerve
Dura mater
(^)
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Learning^
Cengage^
©^
Figure 10- 9 The anatomy of the spinal meninges and the spinal cord.
Health Alert
Spinal TAP
The spinal cord extends down to the sec-ond
lumbar vertebra. Yet spinal nerves, sur-
rounded by the meninges, go all the way down
to the end of the vertebral column. Be-cause
there is no spinal cord at the end of the
vertebral canal, a needle can be inserted into
the subarachnoid space in this area without
damaging the spinal cord. This is done to per-
form a spinal tap and extract cerebrospinal
because they consist of both motor and sensory fibers. Most
of the spinal nerves exit the vertebral column be-tween
adjacent vertebrae. They are named and num-bered
according to the region and level of the spinal cord from
which they emerge (Figure 10-10). There are 8 pairs of
cervical nerves, 12 pairs of thoracic nerves, 5 pairs of
fluid, which can then be -examined for infec-
tious organisms like those causing meningi-tis,
or for detecting blood, in the case of a
hemorrhage. A needle could also be inserted
with an anesthetic agent to administer spinal
anesthesia in this way. If a radiopaque sub-
stance is injected in this area, an X-ray can be
taken of the spinal cord to detect any dam-age
or defects in the cord.
lumbar nerves, 5 pairs of sacral nerves, and a single pair of
coccygeal nerves. The spinal nerves are also num-bered
according to the order (starting superiorly) within the
region. Thus, the 31 pairs are C1 through C8 (cervi-cal), T1
through T12 (thoracic), L1 through L5 (lumbar), S1
through S5 (sacral), and Cx (coccygeal).