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U N I T 1 0
Nervous System
Protection of the Spinal Cord
The spinal cord, spinal nerves, and their supporting
structures are protected by the bony structures of the
vertebral column. The vertebral body is the anterior,
more massive part of the bone that gives strength to
the vertebral column and supports body weight. Each
vertebral body has two pedicles that extend posteriorly
and support the laterally oriented transverse processes
of the laminae, which arch medially and fuse to con-
tinue as the spinal processes. The vertebral arch and
posterior surface of the vertebral body form the wall
of the vertebral foramen which is formed by the union
of the vertebral arch with the vertebral body. The suc-
cession of vertebral foramina in the articulated spinal
column forms the vertebral canal (spinal canal), which
contains the spinal cord, meninges, fat, and spinal nerve
roots. The spaces between the vertebral bodies are filled
with fibrocartilaginous discs and stabilized with tough
ligaments. A gap, the intervertebral foramen, occurs
between each two succeeding pedicles, allowing for
the exit of the segmental nerves and passage of blood
Posterior view
Cervical
nerves
(8 pairs)
Thoracic
nerves
(12 pairs)
Lumbar
nerves
(5 pairs)
Sacral
nerves
(5 pairs)
Coccygeal nerves
T12
T1
C8
L1
L5
S1
S5
C1
Thoracic
Lumbar
Sacral
White matter
Intermediolateral
horn of gray matter
Cervical
entral horn
of gray matter
Dorsal horn
of gray matter
B
Brachial plexus
(C5 T1)
Lumbar plexus
(L1 L4)
Sacral plexus
(L4 S5)
Sciatic nerve
A
Cervical plexus
First cervical vertebrae
First cervical nerve
(C1–C5)
V
FIGURE 34-11.
(A)
Posterior view of the spinal cord, including portions of the major spinal nerves
and some of the components of the major nerve plexuses.
(B)
Cross-sectional views of the spinal
cord, showing regional variations in gray matter and increasing white matter as the cord ascends.
Spinal cord
Dura mater
Arachnoid
Pia mater
Ventral root
Dorsal root
Dorsal root
ganglion
Paired spinal nerves
Vertebrae
FIGURE 34-12.
Spinal cord and meninges.
