Page 383 - Atlas of Histology with Functional Correlations

FIGURE 9.28 ■ Ultrastructure of peripheral nerve fascicle in the PNS cut in the
transverse plane. Courtesy of Dr. Mark DeSantis, Professor Emeritus, WWAMI
Medical Program, University of Idaho, Moscow, ID. Approximately ×25,000.

FIGURE 9.29 | Dorsal Root Ganglion with Dorsal

and Ventral Roots and Spinal Nerve (Longitudinal

Section)

The dorsal root ganglia are aggregations of neuron cell bodies that are located
outside the CNS. The dorsal (posterior) root ganglion (7) is situated on the

dorsal (posterior) nerve root (9), which joins the spinal cord. Numerous round
(pseudo-) unipolar neurons (2), or sensory neurons, constitute the majority of
the ganglion. Fascicles of nerve fibers (3) pass between the unipolar neurons (2)
and course either in the dorsal nerve root (9) or the spinal nerve (5). The nerve
fibers (3) represent the peripheral processes that are formed by the bifurcation of

a single axon that emerges from each unipolar neuron (2).

Each dorsal root ganglion (7) is enclosed by an irregular connective tissue
layer (1) that contains adipose cells, nerves (6), and blood vessels (6). The
connective tissue (1, 6) around the ganglion (7) merges with the epineurium (4)

of the peripheral spinal nerve (5). The nerve fibers in the ventral (anterior) root
(11) join the nerve fibers that emerge from the ganglion (7) to form the spinal
nerve (5). The spinal nerve (5) is formed when the dorsal nerve root (9) and the

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