Porth's Essentials of Pathophysiology, 4e

838

Nervous System

U N I T 1 0

Posterior view

First cervical nerve

First cervical vertebrae

Dorsal horn of gray matter

C1

Cervical nerves (8 pairs)

Cervical plexus

(C1–C5)

T1 C8

entral horn of gray matter V

Cervical

Brachial plexus (C5 T1)

Thoracic nerves (12 pairs)

White matter

Intermediolateral horn of gray matter

Thoracic

T12

L1

Lumbar nerves (5 pairs)

Lumbar plexus (L1 L4) Sacral plexus (L4 S5)

L5

Lumbar

Sacral nerves (5 pairs)

S1

S5

Sciatic nerve

Sacral

Coccygeal nerves

A

B

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.

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

Spinal cord

Dura mater

Ventral root

Dorsal root

Dorsal root ganglion

Arachnoid Pia mater

Vertebrae

Paired spinal nerves

FIGURE 34-12. Spinal cord and meninges.